CN116995234A - Positive electrode sheet, electrochemical device, electronic device, and method for manufacturing positive electrode sheet - Google Patents
Positive electrode sheet, electrochemical device, electronic device, and method for manufacturing positive electrode sheet Download PDFInfo
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- CN116995234A CN116995234A CN202210448313.8A CN202210448313A CN116995234A CN 116995234 A CN116995234 A CN 116995234A CN 202210448313 A CN202210448313 A CN 202210448313A CN 116995234 A CN116995234 A CN 116995234A
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- 125000001436 propyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 1
- 239000002296 pyrolytic carbon Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 229930195734 saturated hydrocarbon Natural products 0.000 description 1
- 150000003346 selenoethers Chemical class 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
- NNMHYFLPFNGQFZ-UHFFFAOYSA-M sodium polyacrylate Chemical compound [Na+].[O-]C(=O)C=C NNMHYFLPFNGQFZ-UHFFFAOYSA-M 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 150000003457 sulfones Chemical class 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- 229910000314 transition metal oxide Inorganic materials 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
Abstract
Embodiments of the present disclosure provide a positive electrode sheet, an electrochemical device, an electronic device, and a method of manufacturing the positive electrode sheet. The positive electrode sheet 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 including a pole piece auxiliary agent represented by formula I, in formula I, R1 has a structure represented by formula II, in formula II, R11 is selected from a substituted or unsubstituted C1-C4 alkyl group, R12, R13, R14, and R15 are each independently selected from any one of a substituted or unsubstituted C1-C4 alkyl group and a substituted or unsubstituted C2-C4 alkenylene group, wherein when substituted, the substituent includes at least one of a C1-C4 alkyl group, a B-O structure-containing group, a P-O structure-containing group, a cyano group, an F atom, and a heteroatom, wherein the heteroatom includes at least one of an O atom, an N atom, a P atom, and an S atom.
Description
Technical Field
Example embodiments of the present disclosure relate generally to the field of energy storage technology, and in particular, to a positive electrode sheet, an electrochemical device, an electronic device, and a method of manufacturing the positive electrode sheet.
Background
With the dramatic decrease in global fossil energy and the increase in greenhouse effect, lithium ion batteries as new energy storage devices are an important form of future energy supply. The lithium ion battery has the advantages of high energy density, low memory effect, long service life and the like, and is widely applied to the fields of digital electric appliances and energy power. Two of the most urgent needs of electric vehicles for power batteries at present are to increase the energy density of the battery core and improve the electrical performance of lithium ion batteries (especially to inhibit high-temperature gas production). Increasing the positive charge voltage and increasing the positive nickel content are conventional means of increasing the energy density of the cell. However, increasing both the positive charge voltage and the positive nickel content can exacerbate the high temperature gas production of the cell in a high state of charge (SOC) state. Therefore, how to suppress high-temperature gas production while improving the energy density of lithium ion batteries is a major problem to be solved.
Disclosure of Invention
It is an object of the present disclosure to provide a positive electrode sheet, an electrochemical device, an electronic device, and a method of manufacturing a positive electrode sheet, which at least partially solve the above-mentioned problems existing in the prior art.
According to a first aspect of the present disclosure, there is provided a positive electrode sheet comprising 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 comprising a pole piece auxiliary agent represented by formula I,
In formula I, R1 has a structure represented by formula II,
in the case of the formula II, the formula,
r11 is selected from a substituted or unsubstituted C1-C4 alkyl group, R12, R13, R14 and R15 are each independently selected from any of a substituted or unsubstituted C1-C4 alkyl group and a substituted or unsubstituted C2-C4 alkenylene group, wherein when substituted, the substituents include at least one of a C1-C4 alkyl group, a B-O structure-containing group, a P-O structure-containing group, a cyano group, a F atom and a heteroatom, wherein the heteroatom includes at least one of an O atom, an N atom, a P atom and a S atom.
In some embodiments, the pole piece additive represented by formula I includes at least one of the pole piece additives represented by formulas I-1 to I-6:
in some embodiments, the mass percentage of the pole piece additive represented by formula I is 0.5% -1.5% based on the total mass of the positive electrode active material layer.
In some embodiments, the positive electrode active material layer further comprises a pole piece aid represented by formula III,
(M x+ ) 3 (PO 4 ) x-type III is used for the treatment of the skin,
in formula III, M is selected from at least one of Li, na, K, cs, ca and Mg.
In some embodiments, the total mass percent content of both the pole piece aid represented by formula I and the pole piece aid represented by formula III is from 0.01% to 10%, based on the total mass of the positive electrode active material layer.
In some embodiments, the mass percentage of the pole piece additive represented by formula I is 0.5% -1.5% based on the total mass of the positive electrode active material layer.
In some embodiments, the mass percentage of the pole piece additive represented by formula III is 1% -7% based on the total mass of the positive electrode active material layer.
In some embodiments, the mass percent of the pole piece aid represented by formula III is greater than the mass percent of the pole piece aid represented by formula I and less than ten times the mass percent of the pole piece aid represented by formula I, based on the total mass of the positive electrode active material layer.
According to a second aspect of the present disclosure, there is provided an electrochemical device including the positive electrode sheet, the negative electrode sheet, the separator, and the electrolyte according to the first aspect of the present disclosure.
According to a third aspect of the present disclosure, there is provided an electronic device comprising an electrochemical device according to the second aspect of the present disclosure.
According to a fourth aspect of the present disclosure, there is provided a method of manufacturing a positive electrode sheet, including:
providing a first slurry including a solvent, and a positive electrode active material, a binder, and a conductive agent dispersed in the solvent;
Adding an additive into the first slurry, stirring to obtain a second slurry, wherein the additive comprises a pole piece auxiliary agent represented by a formula I,
in formula I, R1 has a structure represented by formula II,
in the case of the formula II, the formula,
r11 is selected from substituted or unsubstituted C1-C4 alkyl, R12, R13, R14 and R15 are each independently selected from any of substituted or unsubstituted C1-C4 alkyl and substituted or unsubstituted C2-C4 alkenylene, wherein when substituted, the substituents include at least one of C1-C4 alkyl, a B-O structure-containing group, a P-O structure-containing group, cyano, F atom and a heteroatom, wherein the heteroatom includes at least one of O atom, N atom, P atom and S atom; and
after vacuum defoaming, the second slurry is coated on the surface of a positive electrode current collector and dried to form a positive electrode active material layer on the surface of the positive electrode current collector, thereby obtaining the positive electrode sheet.
In some embodiments, the pole piece additive represented by formula I includes at least one of the pole piece additives represented by formulas I-1 to I-6:
in some embodiments, the pole piece additive represented by formula I is present in an amount of 0.5% to 1.5% by mass based on the total mass of the positive electrode active material, the binder, the conductive agent, and the additive.
In some embodiments, the additive further comprises a pole piece aid represented by formula III,
(M x+ ) 3 (PO 4 ) x-type III is used for the treatment of the skin,
in formula III, M is selected from at least one of Li, na, K, cs, ca and Mg.
In some embodiments, the total mass percent of both the pole piece aid represented by formula I and the pole piece aid represented by formula III is from 0.01% to 10%, based on the total mass of the positive electrode active material, the binder, the conductive agent, and the additive.
In some embodiments, the pole piece additive represented by formula I is present in an amount of 0.5% to 1.5% by mass based on the total mass of the positive electrode active material, the binder, the conductive agent, and the additive.
In some embodiments, the mass percentage of the pole piece auxiliary agent represented by formula III is 1% -7% according to the total mass of the positive electrode active material, the binder, the conductive agent and the additive.
In some embodiments, the mass of the pole piece aid represented by formula III added is greater than the mass of the pole piece aid represented by formula I and less than ten times the mass of the pole piece aid represented by formula I.
In some embodiments, providing the first slurry comprises: mixing and stirring the binder and the solvent at the stirring speed of 10-40rpm for 300-400 minutes to prepare binder glue solution; mixing and stirring the positive electrode active material, the conductive agent and the binder glue solution, wherein the stirring speed is 25-40rpm, and the stirring time is 300-450 minutes; and adding the solvent for the second time and stirring to obtain the first slurry, wherein the stirring speed is 35-40rpm, and the stirring time is 20-120 minutes.
In some embodiments, the stirring speed of the stirring performed after the addition of the additive to the first slurry is 10-20rpm and the stirring time is 10-30 minutes.
In the embodiment according to the disclosure, the electrode sheet auxiliary agent represented by the formula I and the optional electrode sheet auxiliary agent represented by the formula III are introduced in the positive electrode sheet production process, so that the electrode sheet auxiliary agent can form an interfacial film on the surface layer of the positive electrode active material layer in the preparation process of the battery cell. The interface film is rich in ion conducting groups, can form a rapid ion conducting belt, has good mechanical stability at high temperature, and can remarkably inhibit high-temperature gas production. In addition, by combining with the optimization of the formation process in the preparation process of the battery cell, the pole piece auxiliary agent can also become an additional active lithium source, so that the battery capacity is effectively improved.
This content section is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This section is not intended to identify key features or essential features of the disclosure, nor is it intended to be used to limit the scope of the disclosure.
Drawings
The above, as well as additional purposes, features, and advantages of embodiments of the present disclosure will become readily apparent from the following detailed description when read in conjunction with the accompanying drawings. Several embodiments of the present disclosure are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which:
Fig. 1 illustrates a schematic structure of a positive electrode sheet according to an embodiment of the present disclosure.
Detailed Description
In order to make the objects, technical solutions and advantages of the present disclosure more apparent, the technical solutions of the present disclosure will be clearly and completely described in connection with example embodiments. It should be understood that the described embodiments are some, but not all, of the embodiments of the present disclosure. The related embodiments described herein are of illustrative nature and are intended to provide a basic understanding of the present disclosure. The embodiments of the present disclosure should not be construed as limiting the present disclosure. Based on the technical solution provided in the present disclosure and the embodiments given, all other embodiments obtained by a person skilled in the art without making any creative effort are within the scope of protection of the present disclosure.
In this document, a list of items connected by the terms "any of," "any of," or other similar terms may mean any of the listed items. For example, if items A and B are listed, then the phrase "either of A and B" means either only A or only B. In another example, if items A, B and C are listed, then the phrase "any of A, B and C" means only a; only B; or only C. Item a may comprise a single element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements.
In this document, a list of items connected by the terms "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items a and B are listed, the phrase "at least one of a and B" means only a; only B; or A and B. In another example, if items A, B and C are listed, then the phrase "at least one of A, B and C" means only a; or only B; only C; a and B (excluding C); a and C (excluding B); b and C (excluding A); or A, B and C. Item a may comprise a single element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements.
Herein, for simplicity, a "Cn-Cm" group refers to a group having "n" to "m" carbon atoms, where "n" and "m" are integers. For example, "C1-C10" alkyl refers to an alkyl group having 1 to 10 carbon atoms.
In this context, the term "alkyl" is intended to be a straight chain saturated hydrocarbon structure having from 1 to 20 carbon atoms. "alkyl" is also intended to be a branched or cyclic hydrocarbon structure having 3 to 20 carbon atoms. For example, the alkyl group may be an alkyl group of 1 to 20 carbon atoms, an alkyl group of 1 to 10 carbon atoms, an alkyl group of 1 to 5 carbon atoms, an alkyl group of 5 to 20 carbon atoms, an alkyl group of 5 to 15 carbon atoms, or an alkyl group of 5 to 10 carbon atoms. When alkyl groups having a specific carbon number are specified, all geometric isomers having that carbon number are contemplated; thus, for example, reference to "butyl" is intended to include n-butyl, sec-butyl, isobutyl, tert-butyl and cyclobutyl; "propyl" includes n-propyl, isopropyl and cyclopropyl. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, methylcyclopentyl, ethylcyclopentyl, n-hexyl, isohexyl, cyclohexyl, n-heptyl, octyl, cyclopropyl, cyclobutyl, norbornyl, and the like. In addition, the alkyl group may be optionally substituted or unsubstituted.
Herein, the term "alkenylene" encompasses both straight and branched chain alkenylenes. When an alkenylene group having a specific carbon number is specified, all geometric isomers of the alkenylene group having that carbon number are contemplated. For example, the alkenylene group may be an alkenylene group of 2 to 20 carbon atoms, an alkenylene group of 2 to 15 carbon atoms, an alkenylene group of 2 to 10 carbon atoms, an alkenylene group of 2 to 5 carbon atoms, an alkenylene group of 5 to 20 carbon atoms, an alkenylene group of 5 to 15 carbon atoms, or an alkenylene group of 5 to 10 carbon atoms. Representative alkylene groups include, for example, vinylidene, propenylene, butenylene, and the like. In addition, alkenylene groups may be optionally substituted or unsubstituted.
Herein, the term "heteroatom" means an atom other than C, H. For example, the heteroatom may comprise at least one of B, N, O, si, P, S.
In this context, the term "cyano" encompasses organics containing an organic group-CN.
As described hereinabove, two of the most urgent demands of current electric vehicles on power cells are to increase the cell energy density and improve the electrical performance of lithium ion batteries (especially to suppress high temperature gassing).
Many efforts are made in the industry to solve the above problems. For example, measures such as doping and cladding of the surface layer of the positive electrode, optimization of sintering curve, optimization of particle size of particles and the like are adopted for the positive electrode. Some high-temperature gas production inhibition auxiliary agents (such as vinylene carbonate, 1, 3-propylene sultone and the like) are mainly introduced to the electrolyte. The suppression effect of the monocrystalline high-nickel material on the high-temperature gas production of the battery cell is obviously improved, but the monocrystalline material can cause the dynamic performance of the material to be obviously reduced, and meanwhile, the cost is obviously increased. In addition, introducing the gas production inhibition auxiliary agent into the electrolyte can influence the conductivity of the electrolyte, increase interface impedance, deteriorate low-temperature performance, influence electrical properties such as high-rate discharge, cycle life and the like.
In order to solve the above-mentioned problems existing in the prior art, embodiments of the present disclosure provide a positive electrode sheet.
[ Positive electrode sheet ]
Positive electrode sheets are sheet structures known in the art that can be used in electrochemical devices (e.g., lithium ion batteries). Fig. 1 illustrates a schematic structure of a positive electrode sheet according to an embodiment of the present disclosure. As shown in fig. 1, the positive electrode sheet includes a positive electrode current collector 1 and a positive electrode active material layer 2.
The positive electrode current collector 1 is a supporting layer that is conductive and does not react with other components of the electrochemical device. In some embodiments, the positive electrode current collector 1 comprises a metal, including but not limited to aluminum foil.
The positive electrode active material layer 2 is provided on the surface of the positive electrode current collector 1. The positive electrode active material layer 2 contains a positive electrode active material, and may further contain a binder and a conductive agent. The positive electrode active material may be selected from materials known in the art that can be used as an electrochemical device for lithium ion deintercalation.
In some embodiments, the positive electrode active material may be selected from LiMnO 2 、LiMn 2 O 4 、LiNi 1-x Co x O 2 、LiCo 1- x Mn x O 2 、LiNi 1-x Mn x O 2 (0＜x＜1)、Li(Ni x Co y Mn z )O 4 (0＜x＜1，0＜y＜1，0＜z＜1，0＜x+y+z＜1)、LiMn 2-a Ni a O 4 、LiMn 2-a Co a O 4 (0＜a＜2)、LiMPO 4 (M is at least one selected from Co, ni, fe, mn, V), spinel type material LiMn 2 O 4 Layered material lithium cobalt oxide (LiCoO) 2 ) Lithium nickelate (LiNiO) 2 )、Li a Ni x A y B (1-x-y) O 2 (0.95.ltoreq.a.ltoreq.1, A and B may be independently selected from any one of Co, mn, al, and A and B are different, 0 < x < 1,0 < y < 1,0 < x+y < 1). In some embodiments, the positive electrode active material may also include at least one of sulfide, selenide, and halide.
In some embodiments, the positive electrode active material also has a coating layer on its surface, or is mixed with a material having a coating layer. In some embodiments, the coating layer comprises at least one coating element compound selected from oxides, hydroxides, oxyhydroxides, oxycarbonates, hydroxycarbonates of the coating element. In some embodiments, the compound used for the cladding layer may be crystalline or amorphous. In some embodiments, the cladding elements for the cladding layer include Mg, al, co, K, na, ca, si, ti, V, sn, ge, ga, B, as, zr or any mixture thereof. In some embodiments, the coating layer may be formed by any method as long as the properties of the positive electrode active material are not adversely affected by including the element in the compound.
In some embodiments, the positive electrode active material layer 2 further includes a positive electrode binder and a positive electrode conductive agent. The positive electrode binder is used to improve the binding properties of the positive electrode active material particles with each other and with the positive electrode current collector. In some embodiments, the positive electrode binder includes at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an ethyleneoxy-containing polymer, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber of acrylic acid (ester), epoxy resin, nylon. The positive electrode conductive agent is used to provide conductivity to the electrode, and may include any conductive material as long as it does not chemically react with the active material. In some embodiments, the positive electrode conductive agent is at least one of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, metal powder, metal fiber, and polyphenylene derivative. In some embodiments, the metal in the metal powder, metal fibers comprises at least one of copper, nickel, aluminum, silver.
In the embodiments of the present disclosure, the positive electrode active material layer 2 further comprises a first electrode sheet auxiliary agent, i.e. the electrode sheet auxiliary agent represented by formula I,
in formula I, R1 has a structure represented by formula II,
in the case of the formula II, the formula,
r11 is selected from a substituted or unsubstituted C1-C4 alkyl group, R12, R13, R14 and R15 are each independently selected from any of a substituted or unsubstituted C1-C4 alkyl group and a substituted or unsubstituted C2-C4 alkenylene group, wherein when substituted, the substituents include at least one of a C1-C4 alkyl group, a B-O structure-containing group, a P-O structure-containing group, a cyano group, a F atom and a heteroatom, wherein the heteroatom includes at least one of an O atom, an N atom, a P atom and a S atom.
By adding the first pole piece auxiliary agent into the positive electrode active material layer, the impedance of the battery core can be obviously reduced, and the circulation capacity retention rate and the high-temperature storage performance can be improved.
In some embodiments, the first pole piece aid comprises at least one of the pole piece aids represented by formulas I-1 to I-6:
in some embodiments, the first pole piece additive is present in an amount of 0.5% to 1.5% by mass based on the total mass of the positive electrode active material layer 2. In other embodiments, the mass percent of the first pole piece additive may be greater or less, and the scope of the present disclosure is not strictly limited in this respect.
In some embodiments, the positive electrode active material layer 2 further comprises a second pole piece aid, namely a pole piece aid represented by formula III,
(M x+ ) 3 (PO 4 ) x-type III is used for the treatment of the skin,
in formula III, M is selected from at least one of Li, na, K, cs, ca and Mg. For example, the second tablet aid comprises Li 3 PO 4 、Na 3 PO 4 、K 3 PO 4 、Cs 3 PO 4 、Ca 3 (PO4) 2 And Mg (magnesium) 3 (PO4) 2 At least one of them.
In some embodiments, the second pole piece aid comprises at least one of the pole piece aids represented by formulas II-1 and II-2:
Li 3 PO 4 formula II-1, na 3 PO 4 Formula II-2.
By introducing the first pole piece auxiliary agent and the second pole piece auxiliary agent in the production process of the positive pole piece, the pole piece auxiliary agent can form an interface film on the surface layer of the positive pole active material layer in the preparation process of the battery cell. The interface film is rich in ion conducting groups, can form a rapid ion conducting belt, has good mechanical stability at high temperature, and can remarkably inhibit high-temperature gas production. In addition, in combination with formation process optimization in the preparation process of the battery cell, the second electrode slice auxiliary agent comprises Li 3 PO 4 Under the condition of (1), the pole piece auxiliary agent can also become an additional active lithium source, so that the battery capacity is effectively improved.
In some embodiments, the total mass percent of both the first and second sheet aids is 0.01% -10% based on the total mass of the positive electrode active material layer 2. In other embodiments, the total mass percent of both the first and second pole piece additives may be greater or less, the scope of the present disclosure not being strictly limited in this respect.
In some embodiments, the first pole piece additive is present in an amount of 0.5% to 1.5% by mass based on the total mass of the positive electrode active material layer 2. In other embodiments, the mass percent of the first pole piece additive may be greater or less, and the scope of the present disclosure is not strictly limited in this respect.
In some embodiments, the second tablet aid is 1% -7% by mass, based on the total mass of the positive electrode active material layer 2. In other embodiments, the mass percent of the second tablet aid may be greater or less, and the scope of the present disclosure is not strictly limited in this respect.
When the mass of the first pole piece auxiliary agent accounts for 0.5% -1.5% of the mass of the positive electrode active material layer 2 and the mass of the second pole piece auxiliary agent accounts for 1% -7% of the mass of the positive electrode active material layer 2, the reaction activation energy under the high state of charge (SOC) of the positive electrode can be obviously increased, and the gas production is inhibited. However, when the content of the first and second electrode sheet auxiliaries is too high, the ion migration number of the electrolyte itself is significantly deteriorated, the infiltration of the electrolyte into the electrode sheet is deteriorated, and the low-temperature resistance is significantly increased. Therefore, the content of the first and second auxiliary agents in the positive electrode sheet should not be too high.
In some embodiments, the second pole piece additive is greater than the first pole piece additive by weight and less than ten times the first pole piece additive by weight, based on the total mass of the positive active material layer 2. In other words, the mass percent of the second pole piece auxiliary agent and the mass percent of the first pole piece auxiliary agent meet the following relation, wherein 1 is less than the content of the second pole piece auxiliary agent/the content of the first pole piece auxiliary agent is less than 10. This content relationship between the first and second sheet aids ensures that the first and second sheet aids can form a fast ion conductor material at the surface layer of the positive electrode and that the second sheet aid includes Li when high temperature chemical conversion is performed 3 PO 4 In the case of (2), a part of additional lithium source is reserved in the positive electrode, and thus the discharge capacity can be remarkably improved. In addition, the content relation can avoid first effect reduction of the battery core caused by decomposition of the free first pole piece auxiliary agent or the free second pole piece auxiliary agent under the high-temperature formation condition, so that the high-temperature cycle performance can be improved.
Embodiments of the present disclosure also provide a method of manufacturing a positive electrode sheet, which may be used to manufacture the positive electrode sheet as described above. The method comprises the following steps: providing a first slurry including a solvent, a positive electrode active material dispersed in the solvent, a binder, and a conductive agent; adding an additive into the first slurry, and stirring to obtain a second slurry; and coating the second slurry on the surface of the positive electrode current collector after vacuum defoaming, and drying to form a positive electrode active material layer on the surface of the positive electrode current collector, thereby obtaining a positive electrode sheet. In addition, in some embodiments, the obtained positive plate may be rolled, slit, cut, etc. to obtain a desired target plate.
The positive electrode active material, the conductive agent, and the binder in the first slurry may be of various types described hereinabove, and will not be described in detail herein. In one embodiment, the mass ratio of the positive electrode active material, the conductive agent, and the binder may be (92-98): (0.4-4): (0.5-4). In other embodiments, the positive electrode active material, the conductive agent, and the binder may have other mass ratios, and the scope of the present disclosure is not strictly limited in this respect. Furthermore, in one embodiment, N-methylpyrrolidone (NMP) may be used as a solvent. In other embodiments, other types of solvents may be employed, and the scope of the present disclosure is not strictly limited in this respect.
In some embodiments, the first slurry may be provided by: (1) Mixing and stirring a solvent (such as NMP) and a binder at a stirring speed of 10-40 revolutions per minute (rpm) for 300-400 minutes (min) to obtain a binder glue solution; (2) Mixing the positive electrode active material, the conductive agent and the adhesive glue solution, and uniformly stirring at a stirring speed of 25-40rpm and a dispersing speed of 2000-3000rpm for 300-450min; and (3) adding a solvent (NMP) into the mixture obtained in the step (2) for the second time, uniformly stirring, wherein the stirring speed is 35-40rpm, the dispersing speed is 1800-3300rpm, and the stirring time is 20-120min, so as to obtain first slurry. In other embodiments, the first slurry may be obtained by other preparation processes, and the scope of the present disclosure is not strictly limited in this respect.
In some embodiments, during the stirring after adding the additive to the first slurry at a specific mass fraction, low-speed stirring is performed at a stirring speed of 10 to 20rpm for a stirring time of 10 to 30 minutes, thereby obtaining the second slurry. The pole piece auxiliary agent contacted with the stirring paddle can be prevented from being decomposed due to temperature rise by adopting low-speed stirring.
It should be appreciated that in other embodiments, other manufacturing processes may be employed to manufacture the positive plate, and the scope of the present disclosure is not strictly limited in this respect.
The type and quality of the additives added to the first slurry will be described below.
In some embodiments, the additive comprises a pole piece aid represented by formula I,
in formula I, R1 has a structure represented by formula II,
in the case of the formula II, the formula,
r11 is selected from a substituted or unsubstituted C1-C4 alkyl group, R12, R13, R14 and R15 are each independently selected from any of a substituted or unsubstituted C1-C4 alkyl group and a substituted or unsubstituted C2-C4 alkenylene group, wherein when substituted, the substituents include at least one of a C1-C4 alkyl group, a B-O structure-containing group, a P-O structure-containing group, a cyano group, a F atom and a heteroatom including at least one of an O atom, an N atom, a P atom and a S atom.
In some embodiments, the pole piece aid represented by formula I includes at least one of the pole piece aids represented by formulas I-1 through I-6:
in some embodiments, the mass percent content of the pole piece aid represented by formula I is 0.5% -1.5% based on the total mass of the positive electrode active material, binder, conductive agent and additive.
In some embodiments, the additive further comprises a pole piece aid represented by formula III,
(M x+ ) 3 (PO 4 ) x-type III is used for the treatment of the skin,
in formula III, M is selected from at least one of Li, na, K, cs, ca and Mg.
In some embodiments, the total mass percent of both the pole piece aid represented by formula I and the pole piece aid represented by formula III is from 0.01% to 10%, based on the total mass of the positive electrode active material, binder, conductive agent, and additive.
In some embodiments, the mass percent content of the pole piece aid represented by formula I is 0.5% -1.5% based on the total mass of the positive electrode active material, binder, conductive agent and additive.
In some embodiments, the mass percent content of the pole piece aid represented by formula III is 1% -7% based on the total mass of the positive electrode active material, the binder, the conductive agent and the additive.
In some embodiments, the mass of the pole piece aid represented by formula III added to the first slurry is greater than the mass of the pole piece aid represented by formula I and less than ten times the mass of the pole piece aid represented by formula I.
[ electrochemical device ]
Embodiments of the present disclosure provide an electrochemical device, such as a primary battery or a secondary battery. The secondary battery is, for example, a lithium ion battery, a sodium ion battery, a zinc ion battery, or a supercapacitor. In the embodiments of the present disclosure, the principles of the present disclosure are described only with lithium ion batteries as examples, but the scope of the present disclosure is not limited thereto.
The electrochemical device includes the positive electrode sheet of the embodiments of the present disclosure, and the structure and composition of the positive electrode sheet will not be described herein. In addition, the electrochemical device may further include an electrolyte, a negative electrode sheet, a separator, a case, and the like.
1. Electrolyte solution
The electrolyte contains an organic solvent and an electrolyte. In some embodiments, the electrolyte may also include additional additives.
1. Organic solvents
In the embodiments according to the present disclosure, there is no particular limitation on the kind of the organic solvent, and it may be selected and customized according to the system requirements. For example, nonaqueous organic solvent systems may be employed. The nonaqueous organic solvent system may include any of a variety of carbonate, carboxylate, nitrile, sulfone, and ether solvents. The carbonates may include cyclic carbonates and chain carboxylates, and halogenated derivatives thereof, or mixtures thereof in any ratio. Specifically, the organic solvent may be at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylethyl carbonate, methyl formate, ethyl acetate, propyl propionate, ethyl propionate, γ -butyrolactone, and tetrahydrofuran. It should be understood that various other types of organic solvents are also possible, and the scope of the present disclosure is not strictly limited in this respect.
2. Electrolyte composition
In embodiments according to the present disclosure, the electrolyte may be of various useful types, such as a solid electrolyte, a gel electrolyte, or a liquid electrolyte.
In one embodiment, when the electrolyte is a liquid electrolyte, the mass of the liquid electrolyte may be 5% -23% of the total mass of the electrolyte. Preferably, the mass of the liquid electrolyte may be 9% -16% of the total weight of the electrolyte. In one embodiment, the liquid electrolyte may be selected from at least one of lithium salt and sodium salt. The kind of lithium salt is not particularly limited and may be selected according to actual demands. Preferably, the lithium salt may include at least LiPF 6 . The lithium salt may further comprise LiBF 4 、LiClO 4 、LiAsF 6 、LiBOB、LiDFOB、LiFSI、LiTFSI、LiPO 2 F 2 、LiTFOP、LiN(SO 2 RF) 2 、LiN(SO 2 F)(SO 2 RF), wherein rf=c n F 2n+1 Represents a perfluoroalkyl group, and n is an integer of 1 to 10. The type of sodium salt is not particularly limited, and can be selected according to actual requirements. Preferably, the sodium salt may be selected from the group consisting of NaPF 6 、NaBF 4 、NaClO、NaAsF 6 、NaCF 3 SO 3 、NaN(CF 3 SO 2 ) 2 、NaN(C 2 F 5 SO 2 ) 2 、NaN(FSO 2 ) 2 At least one of them. In other embodiments, the liquid electrolyte may be of other types than lithium and sodium salts, and the scope of the present disclosure is not strictly limited in this respect.
Similarly, in embodiments according to the present disclosure, there is also no strict limitation on the type of solid electrolyte and gel electrolyte, and various conventional or future available solid electrolytes and gel electrolytes are possible.
2. Negative plate
The negative electrode sheet is a negative electrode sheet that can be used in an electrochemical device, as known in the art. In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer.
The negative electrode current collector is a supporting layer that is conductive and does not react with other components of the electrochemical device. In some embodiments, the negative current collector comprises a metal, including but not limited to copper foil.
The anode active material layer is disposed on the surface of the anode current collector. The anode active material layer contains an anode active material. The negative electrode active material may be selected from various negative electrode active materials known in the art that can be used as an electrochemical device. The active material includes, for example, a material capable of reversibly intercalating and deintercalating active ions or a material capable of reversibly doping and deintercalating active ions.
In some embodiments, the negative electrode active material includes at least one of lithium metal, a lithium metal alloy, a carbon material, and a silicon-based material. In some embodiments, the lithium metal alloy comprises lithium and optionallyAn alloy of metals from Na, K, rb, cs, fr, be, mg, ca, sr, si, sb, in, zn, ba, ra, ge, al, sn. The carbon material may be selected from various carbon materials known in the art that can be used as a carbon-based anode active material of an electrochemical device. In some embodiments, the carbon material comprises at least one of crystalline carbon, amorphous carbon. In some embodiments, the crystalline carbon is natural graphite or synthetic graphite. In some embodiments, the crystalline carbon is amorphous, plate-shaped, platelet-shaped, spherical, or fibrous in shape. In some embodiments, the crystalline carbon is a low crystalline carbon or a high crystalline carbon. In some embodiments, the low crystalline carbon comprises at least one of soft carbon, hard carbon. In some embodiments, the high crystalline carbon comprises at least one of natural graphite, crystalline graphite, pyrolytic carbon, mesophase pitch-based carbon fibers, mesophase carbon microbeads, mesophase pitch, high temperature calcined carbon. In some embodiments, the high temperature calcined carbon is petroleum or coke derived from coal tar pitch. In some embodiments, the amorphous carbon comprises at least one of soft carbon, hard carbon, mesophase pitch carbonized product, and fired coke. In some embodiments, the anode active material comprises a transition metal oxide. In some embodiments, the anode active material comprises Si, siO x (0 < x < 2), si/C composite, si-Q alloy, sn, snO z At least one of Sn-C compound and Sn-R alloy, wherein Q is at least one selected from alkali metals, alkaline earth metals, 13 th to 16 th group elements, transition elements and rare earth elements, and Q is not Si, R is at least one selected from alkali metals, alkaline earth metals, 13 th to 16 th group elements, transition elements and rare earth elements, and R is not Sn. In some embodiments, Q and R comprise at least one of Mg, ca, sr, ba, sc, Y, ti, zr, hf, rf, V, nb, ta, db, cr, mo, W, sg, tc, re, bh, fe, pb, ru, os, hs, rh, ir, pd, pt, cu, ag, au, zn, cd, B, al, ga, sn, in, tl, ge, P, as, sb, bi, S, se, te, po.
In some embodiments, the anode active material layer further comprises an anode binder and an anode conductive agent. In some embodiments, the negative electrode binder comprises at least one of a vinylidene fluoride-hexafluoropropylene copolymer (PVDF-Co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an ethyleneoxy-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber of acrylic acid (ester), epoxy resin, nylon. In some embodiments, the negative electrode conductive agent is used to provide conductivity to the electrode, and may comprise any conductive material so long as it does not react with other components of the electrochemical device. In some embodiments, the negative electrode conductive agent comprises any one of a carbon-based material, a metal-based material, a conductive polymer, or a mixture thereof. In some embodiments, the carbon-based material comprises at least one of natural graphite, synthetic graphite, carbon black, acetylene black, ketjen black, carbon fiber. In some embodiments, the metal-based material comprises at least one of a metal powder or metal fiber of copper, nickel, aluminum, silver, or the like. In some embodiments, the conductive polymer comprises a polyphenylene derivative.
In some embodiments, the method of preparing the negative electrode sheet is a method of preparing a negative electrode sheet that can be used in an electrochemical device, as is known in the art. In some embodiments, in the preparation of the anode slurry, a solvent is generally added, and the anode active material is added to a binder and, if necessary, a conductive material and a thickener, and then dissolved or dispersed in the solvent to prepare the anode slurry. The solvent is volatilized during the drying process. The solvent is a solvent known in the art that can be used as the anode active material layer, and includes, but is not limited to, water. The thickener is a thickener known in the art to be useful as a negative electrode active material layer, and includes, but is not limited to, sodium carboxymethyl cellulose.
The embodiment of the present disclosure is not particularly limited in the mixing ratio of the anode active material, the binder, and the thickener in the anode active material layer, and the mixing ratio thereof may be controlled according to desired electrochemical device performance.
In some embodiments, the negative electrode sheet may be prepared using the following procedure:
the negative electrode active material artificial graphite, a conductive agent Super-P, a thickener sodium carboxymethyl cellulose (CMC) and a binder styrene-butadiene rubber are mixed according to the mass ratio of 96.2:2:0.8:1, mixing, adding deionized water, and obtaining negative electrode slurry under the action of a vacuum stirrer, wherein the solid content of the negative electrode slurry is 54wt%;
Uniformly coating the negative electrode slurry on a negative electrode current collector copper foil;
and (3) drying the coated copper foil at high temperature, cold pressing, cutting and slitting, and then drying for 12 hours under the vacuum condition at 120 ℃ to obtain the negative plate.
3. Isolation film
Separator membranes are well known in the art as separator membranes that can be used in electrochemical devices, including but not limited to microporous membranes of the polyolefin type. In some embodiments, the barrier film comprises at least one of Polyethylene (PE), ethylene-propylene copolymer, polypropylene (PP), ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-methacrylate copolymer.
In some embodiments, the separator is a single layer separator or a multilayer separator.
In some embodiments, the separator is coated with a coating. In some embodiments, the coating comprises at least one of an organic coating and an inorganic coating, wherein the organic coating is selected from at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyimide, acrylonitrile-butadiene copolymer, acrylonitrile-styrene-butadiene copolymer, polymethyl methacrylate, polymethyl acrylate, polyethyl acrylate, acrylic-styrene copolymer, polydimethylsiloxane, sodium polyacrylate, sodium carboxymethyl cellulose, and the inorganic coating is selected from SiO 2 、Al 2 O 3 、CaO、TiO 2 、ZnO 2 、MgO、ZrO 2 、SnO 2 At least one of them.
The embodiment of the present disclosure is not particularly limited in terms of the form and thickness of the separator. The method of preparing the separator is a method of preparing a separator that can be used in an electrochemical device, which is well known in the art.
In embodiments according to the present disclosure, one may employThe release film was prepared as follows: selecting polyethylene isolating film with thickness of 9um, passing through PVDF slurry and inorganic particles (sheet boehmite and Al) 2 O 3 The mass ratio of (2) is 70:30 And (3) coating and drying the slurry to obtain the final isolating film, wherein the thickness of the coating is 3um, and the porosity of the membrane is 55%.
4. Preparation of electrochemical device
In some embodiments, an electrochemical device (e.g., a lithium-ion battery) may be prepared using the following procedure: sequentially stacking the positive plate, the isolating film and the negative plate, so that the isolating film is positioned between the positive plate and the negative plate to play a role in isolation; then winding the positive plate, the isolating film and the negative plate to obtain a bare cell, welding the tab, and placing the obtained bare cell in an aluminum-plastic film of an outer package; the electrolyte according to the embodiment of the present disclosure is injected into the dried bare cell, and the target cell, i.e., the electrochemical device, is obtained through the processes of vacuum packaging, standing, formation (e.g., 0.02C constant current to 3.3V, and then 0.1C constant current to 3.6V), shaping, capacity testing, and the like. In other embodiments, other processes may be employed to fabricate the electrochemical device, and the scope of the present disclosure is not strictly limited in this respect.
[ test of Electrical Properties of electrochemical device ]
Hereinafter, the electrical performance test results of the electrochemical device will be described using a lithium ion battery as an example. The lithium ion battery comprises a positive plate, a negative plate, a separation film and electrolyte according to the embodiment of the disclosure.
In the examples and comparative examples described below, reagents, materials and instruments used were commercially available or synthetically obtained unless otherwise specified. The materials specifically used for the positive electrode active material layer in the positive electrode sheet are as follows:
the first pole piece auxiliary agent:
second tablet auxiliary agent: li (Li) 3 PO 4 Formula II-1, na 3 PO 4 Formula II-2;
positive electrode active material: li (Ni) 0.8 Co 0.1 Mn 0.1 )O 2 ；
Conductive agent: super-P;
and (2) a binder: polyvinylidene fluoride.
Both the first and second pole piece additives are commercially available or may be synthetically obtained by methods of preparation well known and conventional in the art.
The lithium ion batteries of examples 1 to 14 and comparative examples 1 to 7 in tables 1 to 3 described below can each be produced according to the following method.
(1) Preparation of a positive plate: mixing and stirring a solvent (such as NMP) and a binder in an environment with humidity lower than 10% and temperature of 20-30 ℃ at a stirring speed of 10-40rpm for 300-400min to obtain a binder glue solution; (2) Mixing the positive electrode active material, the conductive agent and the adhesive glue solution, and uniformly stirring at a stirring speed of 25-40rpm and a dispersing speed of 2000-3000rpm for 300-450min; (3) Adding a solvent (NMP) to the mixture obtained in the step (2) for a second time, and stirring uniformly at a stirring speed of 35-40rpm, a dispersing speed of 1800-3300rpm, and a stirring time of 20-120min to obtain a first slurry, wherein the solid content of the slurry is 72wt%, and the active material Li (Ni 0.8 Co 0.1 Mn 0.1 )O 2 The mass ratio of the conductive agent Super-P to the binder polyvinylidene fluoride is 96:2.2:1.8; (4) Adding an additive with specific mass fraction into the first slurry, uniformly stirring at a low speed, wherein the stirring speed is 10-20rpm, and the stirring time is 10-30 minutes, so as to obtain a second slurry; (5) After vacuum defoaming, the second slurry is coated on the surface of the positive electrode current collector and dried to form a positive electrode active material layer on the surface of the positive electrode current collector, thereby obtaining a positive electrode sheet. In addition, the obtained positive plate can be subjected to rolling, slitting, cutting and other treatments to obtain the required target plate, wherein the coating surface density of the target plate is 14.0mg/cm 2 Compacting 3.3g/cm 3 。
(2) Preparing a negative plate: the negative electrode active material artificial graphite, a conductive agent Super-P, a thickener sodium carboxymethyl cellulose (CMC) and a binder styrene-butadiene rubber are mixed according to the mass ratio of 96.2:2:0.8:1, mixing, adding deionized water, and obtaining negative electrode slurry under the action of a vacuum stirrer, wherein the solid content of the negative electrode slurry is 54wt%; uniformly coating the negative electrode slurry on a negative electrode current collector copper foil; and (3) drying the coated copper foil at high temperature, cold pressing, cutting and slitting, and then drying for 12 hours under the vacuum condition at 120 ℃ to obtain the negative plate.
(3) Preparation of electrolyte: in a dry argon glove box, an organic solvent (EC/DEC/emc=3/2/5, according to mass ratio), additives, lithium salt electrolyte were mixed according to the desired content. Specifically, an organic solvent is firstly added into a dry argon glove box, then an additive is added, the lithium salt electrolyte is added after dissolution and full stirring, and the electrolyte is obtained after uniform mixing.
(4) Preparation of a separation film: selecting polyethylene isolating film with thickness of 9um, passing through PVDF slurry and inorganic particles (sheet boehmite and Al) 2 O 3 The mass ratio of (2) is 70:30 And (3) coating and drying the slurry to obtain the final isolating film, wherein the thickness of the coating is 3um, and the porosity of the membrane is 55%.
(5) Preparation of a lithium ion battery: sequentially stacking the positive plate, the isolating film and the negative plate, so that the isolating film is positioned between the positive plate and the negative plate to play a role in isolation; then winding the positive plate, the isolating film and the negative plate to obtain a bare cell, welding the tab, and placing the obtained bare cell in an aluminum-plastic film of an outer package; the electrolyte according to the embodiment of the disclosure is injected into the dried bare cell, and the target cell is obtained through the procedures of vacuum packaging, standing, formation (for example, 0.02C constant current is filled to 3.3V, and then 0.1C constant current is filled to 3.6V), shaping, capacity testing and the like.
In examples 1 to 14 and comparative examples 1 to 7, the kinds and contents of the first and second electrode sheet assistants used are shown in tables 1, 2 and 3, wherein the content of each electrode sheet assistant is a weight percentage calculated based on the total mass of the positive electrode active material layer.
Next, a performance test process and test results of the lithium ion battery are described.
1. And (3) testing the capacity of the battery cell:
charging the lithium ion battery to 3.3V at a constant current of 0.02C, charging to 3.6V at a constant current of 0.1C, charging to 4.2V at a constant current of 0.2C, standing for 15min, discharging to 3.0V at a constant current of 0.2C, and recording the discharge capacity D of the step Capacity of 。
2. High temperature cycle test of lithium ion battery:
the lithium ion battery is placed in a constant temperature oven at 45 ℃, is charged to 4.2V at a constant current of 2.0 ℃, is charged to 0.05C at a constant voltage, is kept stand for 5min, is discharged to 3.0V at a constant current of 1C, and is kept stand for 10min, so that the lithium ion battery is used as a cycle. The discharge capacity at the initial cycle was designated as C0, and the discharge capacity at 1000 cycles of the battery was designated as C1000.
The capacity retention (%) =c1000/c0×100% after 1000 cycles of lithium ion battery at 45 ℃.
3. High temperature storage test of lithium ion battery:
before storage, the lithium ion battery is charged to 3.65V at a constant current of 0.5C, then the thickness of the lithium ion battery is tested by using a plate thickness meter to obtain the thickness L1, the constant current of 0.5C is charged to 4.2V, the constant voltage is charged to 0.05C, then the lithium ion battery is placed in a high-temperature oven at 60 ℃ for storage for 30 days, and the thickness L30 of the lithium ion battery is measured again after the lithium ion battery is cooled.
The thickness increase rate of the high-temperature storage battery cell of the lithium ion battery is = (L30-L1)/L1 is 100%.
4. DCR test of lithium ion battery:
placing the lithium ion battery in a constant temperature box at 25 ℃ for 2 hours, charging the lithium ion battery to 4.2V at a constant current of 0.5 ℃, charging the lithium ion battery to 0.05C at a constant voltage, standing for 5min, discharging the lithium ion battery to 3.0V at a constant current of 0.1C, and recording the lithium ion battery as capacity C 2 At 0.2C 2 Constant current discharge for 2.5h, recording end voltage U0,1C 2 Discharge for 1s (second), and record terminal voltage U1.
The calculation formula of the direct current internal resistance DCR of the lithium ion battery is as follows: dcr= (U0-U1)/(0.9C) 2 )。
Table 1 below shows the cell capacity test results for various lithium ion batteries. In various lithium ion batteries, the content of the first and second sheet aids refers to mass percent relative to the total mass of the positive electrode active material layer. In comparative example 1, the content of both the first and second sheet auxiliaries was 0, i.e., the first and second sheet auxiliaries were not added to the positive electrode active material layer, and the cell capacity at this time was 3200mAh; in comparative example 2, the first pole piece additive represented by formula I-2 was used in an amount of 0.05% and the second pole piece additive was used in an amount of 0, at which time the cell capacity was 3205mAh; in comparative example 5, the second sheet auxiliary agent represented by formula II-1 was used in an amount of 0.02%, while the first sheet auxiliary agent was used in an amount of 0, and the cell capacity at this time was 3200mAh; in example 1, the first pole piece auxiliary agent represented by the formula I-2 is adopted, the content is 0.1%, the second pole piece auxiliary agent represented by the formula II-1 is adopted, the content is 0.1%, and the capacity of the battery cell at the moment is 3205mAh; in example 14, the first sheet auxiliary agent represented by formula I-5 was used in an amount of 1%, and the second sheet auxiliary agent represented by formula II-1 was used in an amount of 5%, and the cell capacity at this time was 3260mAh. The types and amounts of the first and second tab aids and the corresponding cell capacities in other examples and comparative examples are shown in table 1 in the same manner, and will not be described again here.
Table 1 results of cell capacity test of lithium ion batteries
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The cell capacity data of comparative examples 1 to 4 in table 1 show that the first pole piece auxiliary agent can form a film on the surface of the electrode preferentially compared with the solvent, the film forming efficiency is higher, the lithium loss in the formation process can be effectively reduced, the cell capacity is improved, but the local coordination environment of the surface layer of the electrode is changed due to the high content of the first pole piece auxiliary agent, and the side reaction degree is increased. Comparative examples 5 to 7 show that Li 3 PO 4 Can provide an additional high-efficiency lithium sourceIncreasing discharge capacity, increasing energy density, but high Li content 3 PO 4 Localized deposition can easily occur, resulting in increased localized polarization, which reduces the usable capacity of the positive electrode. Comparison of the cell capacity data of examples 1-14 with the cell capacity data of comparative examples 1-7 shows that the specific proportion of the first pole piece auxiliary agent and the second pole piece auxiliary agent can significantly improve the cell discharge capacity and improve the energy density. In particular, example 8, compared to other examples and comparative examples, can achieve the highest cell capacity of 3262mAh.
Table 2 below shows the capacity retention after 1000 cycles of various lithium ion batteries. In various lithium ion batteries, the content of the first and second sheet aids refers to mass percent relative to the total mass of the positive electrode active material layer. In comparative example 1, the contents of the first and second sheet assistants were both 0, i.e., the first and second sheet assistants were not added to the positive electrode active material layer, at which time the capacity retention rate was 81%; in comparative example 2, the first sheet auxiliary represented by formula I-2 was used in an amount of 0.05%, and the second sheet auxiliary was used in an amount of 0, at which time the capacity retention rate was 82%; in comparative example 5, the second sheet auxiliary represented by formula II-1 was used in an amount of 0.02%, while the first sheet auxiliary was used in an amount of 0, at which time the capacity retention was 81%; in example 1, the first sheet auxiliary agent represented by formula I-2 was used in an amount of 0.1%, and the second sheet auxiliary agent represented by formula II-1 was used in an amount of 0.1%, at which time the capacity retention rate was 83%; in example 14, the first sheet auxiliary represented by formula I-5 was used in an amount of 1%, and the second sheet auxiliary represented by formula II-1 was used in an amount of 5%, at which time the capacity retention was 90%. The types and amounts of the first and second sheet aids and the corresponding capacity retention rates in other examples and comparative examples are shown in table 2 in the same manner and will not be described again.
Table 2 capacity retention of lithium ion batteries
The high-temperature cycle capacity retention data of comparative examples 1 to 7 and examples 1 to 14 in table 2 show that both the first and second sheet aids significantly improved the high-temperature cycle capacity retention, and that the cycle capacity retention was higher when both were used in combination; the first pole piece auxiliary agent can form a fast ion conductor interface film, so that the polarization of the positive pole is obviously reduced, the oxidation activity of the positive pole is reduced, and the gas production reaction of the electrolyte and the positive pole is inhibited; the second tablet auxiliary agent can reduce the lithium removal depth of the positive electrode, reduce the oxidation activity of the positive electrode, inhibit the reaction depth of the electrolyte and the positive electrode, and also play a role of a physical barrier to the electrolyte. Comparison of the retention rate data of examples 1-14 with the retention rate data of comparative examples 1-7 shows that the first pole piece auxiliary agent and the second pole piece in specific proportions can synergistically act to form an organic-inorganic composite interface film, inhibit surface phase transition of the positive electrode and lithium loss of the negative electrode, and improve cycle performance. In particular, example 8 can achieve the highest capacity retention rate compared with other examples and comparative examples, and thus can maximally improve cycle performance.
Table 3 below shows the thickness retention of various lithium ion batteries stored at 60 ℃ for 30 days and the DCR test results at 25 ℃ at 50% state of charge. In various lithium ion batteries, the content of the first and second sheet aids refers to mass percent relative to the total mass of the positive electrode active material layer. In comparative example 1, the contents of the first and second sheet assistants were both 0, i.e., the first and second sheet assistants were not added to the positive electrode active material layer, at which time the thickness increase rate was 25%, and the DCR was 44 milliohms (mohm); in comparative example 2, the first pole piece additive represented by formula I-2 was used in an amount of 0.05%, while the second pole piece additive was used in an amount of 0, at which time the thickness increase rate was 24%, and the DCR was 42mohm; in comparative example 5, the second sheet auxiliary represented by formula II-1 was used in an amount of 0.02%, while the first sheet auxiliary was used in an amount of 0, at which time the thickness increase rate was 24% and the DCR was 43mohm; in example 1, the first sheet auxiliary represented by formula I-2 was used in an amount of 0.1%, and the second sheet auxiliary represented by formula II-1 was used in an amount of 0.1%, at which time the thickness increase rate was 21%, and the DCR was 39mohm; in example 14, the first pole piece additive represented by formula I-5 was used in an amount of 1%, and the second pole piece additive represented by formula II-1 was used in an amount of 5%, at which time the thickness increase rate was 12% and the DCR was 32mohm. The types and amounts of the first and second sheet aids and the corresponding thickness increase rates and DCR in other examples and comparative examples are shown in table 3 in the same manner and will not be described again here.
TABLE 3 thickness retention and DCR test results for lithium ion batteries
The thickness retention and DCR data for comparative examples 1-7 and examples 1-14 in table 3 show that both the first and second pole piece additives reduce the thickness growth rate while reducing the resistance over the range of implementation. The comparison of the thickness retention rate and the DCR data of examples 1-14 with those of comparative examples 1-7 shows that the composite interface film formed by the first pole piece auxiliary agent and the second pole piece auxiliary agent is rich in P and S ion conduction functional groups, has higher high-temperature stability while rapidly transmitting lithium ions, remarkably inhibits the high-temperature high-SOC storage gas production of the battery cell, and simultaneously can greatly reduce the impedance of the battery cell. Especially example 8, the lowest DCR and thickness increase rate can be achieved compared to other examples and comparative examples.
[ electronic device ]
Embodiments of the present disclosure also provide an electronic device that may be any electronic device including, but not limited to, an automobile, a motorcycle, a skateboard, an airplane, a passenger car, a motor, a backup power source, a household large-sized battery, a lithium ion capacitor, a computer, a cell phone, an electronic book, a facsimile machine, a copier, a flash lamp, a television, a VR, an AR, and the like. Note that the electrochemical device of the embodiments of the present disclosure is applicable to, in addition to the above-described electronic devices as examples, electronic devices such as energy storage power stations, marine vehicles, air vehicles, and the like. The air vehicle comprises an air vehicle within the atmosphere and an air vehicle outside the atmosphere.
The electronic device of the embodiments of the present disclosure may include the electrochemical device as described above.
The foregoing description of the embodiments of the present disclosure has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described. The terminology used herein was chosen in order to best explain the principles of the embodiments, the practical application, or the technical improvement in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.
Claims (20)
1. The positive plate comprises a positive current collector and a positive active material layer arranged on the surface of the positive current collector, wherein the positive active material layer comprises a pole piece auxiliary agent represented by a formula I,
in formula I, R1 has a structure represented by formula II,
in the case of the formula II, the formula,
r11 is selected from a substituted or unsubstituted C1-C4 alkyl group, R12, R13, R14 and R15 are each independently selected from any of a substituted or unsubstituted C1-C4 alkyl group and a substituted or unsubstituted C2-C4 alkenylene group, wherein when substituted, the substituents include at least one of a C1-C4 alkyl group, a B-O structure-containing group, a P-O structure-containing group, a cyano group, a F atom and a heteroatom, wherein the heteroatom includes at least one of an O atom, an N atom, a P atom and a S atom.
2. The positive electrode sheet of claim 1, wherein the sheet auxiliary represented by formula I comprises at least one of sheet auxiliary represented by formulas I-1 to I-6:
3. the positive electrode sheet according to claim 1, wherein the mass percentage of the sheet auxiliary agent represented by formula I is 0.5% to 1.5% based on the total mass of the positive electrode active material layer.
4. The positive electrode sheet according to claim 1, wherein the positive electrode active material layer further comprises a sheet auxiliary agent represented by formula III,
(M x+ ) 3 (PO 4 ) x-type III is used for the treatment of the skin,
in formula III, M is selected from at least one of Li, na, K, cs, ca and Mg.
5. The positive electrode sheet according to claim 4, wherein the total mass percentage content of both the electrode sheet auxiliary agent represented by formula I and the electrode sheet auxiliary agent represented by formula III is 0.01 to 10% according to the total mass of the positive electrode active material layer.
6. The positive electrode sheet according to claim 5, wherein the mass percentage of the sheet auxiliary agent represented by formula I is 0.5% to 1.5% based on the total mass of the positive electrode active material layer.
7. The positive electrode sheet according to claim 5, wherein the mass percentage of the sheet auxiliary agent represented by formula III is 1 to 7% based on the total mass of the positive electrode active material layer.
8. The positive electrode sheet according to claim 5, wherein the mass percent content of the electrode sheet auxiliary represented by the formula III is greater than the mass percent content of the electrode sheet auxiliary represented by the formula I and less than ten times the mass percent content of the electrode sheet auxiliary represented by the formula I, based on the total mass of the positive electrode active material layer.
9. An electrochemical device comprising the positive electrode sheet, the negative electrode sheet, the separator, and the electrolyte according to any one of claims 1 to 8.
10. An electronic device comprising the electrochemical device according to claim 9.
11. A method of manufacturing a positive electrode sheet, comprising:
providing a first slurry including a solvent, and a positive electrode active material, a binder, and a conductive agent dispersed in the solvent;
adding an additive into the first slurry, stirring to obtain a second slurry, wherein the additive comprises a pole piece auxiliary agent represented by a formula I,
in formula I, R1 has a structure represented by formula II,
in the case of the formula II, the formula,
r11 is selected from substituted or unsubstituted C1-C4 alkyl, R12, R13, R14 and R15 are each independently selected from any of substituted or unsubstituted C1-C4 alkyl and substituted or unsubstituted C2-C4 alkenylene, wherein when substituted, the substituents include at least one of C1-C4 alkyl, a B-O structure-containing group, a P-O structure-containing group, cyano, F atom and a heteroatom, wherein the heteroatom includes at least one of O atom, N atom, P atom and S atom; and
After vacuum defoaming, the second slurry is coated on the surface of a positive electrode current collector and dried to form a positive electrode active material layer on the surface of the positive electrode current collector, thereby obtaining the positive electrode sheet.
12. The manufacturing method of claim 11, wherein the pole piece aid represented by formula I comprises at least one of pole piece aids represented by formulas I-1 to I-6:
13. the production method according to claim 11, wherein the mass percentage of the pole piece auxiliary agent represented by the formula I is 0.5% to 1.5% based on the total mass of the positive electrode active material, the binder, the conductive agent, and the additive.
14. The method of manufacturing according to claim 11, wherein the additive further comprises a pole piece aid represented by formula III,
(M x+ ) 3 (PO 4 ) x-type III is used for the treatment of the skin,
in formula III, M is selected from at least one of Li, na, K, cs, ca and Mg.
15. The manufacturing method according to claim 14, wherein a total mass percentage of both the pole piece auxiliary agent represented by formula I and the pole piece auxiliary agent represented by formula III is 0.01% to 10% based on a total mass of the positive electrode active material, the binder, the conductive agent, and the additive.
16. The manufacturing method according to claim 15, wherein the mass percentage of the pole piece auxiliary agent represented by the formula I is 0.5% to 1.5% based on the total mass of the positive electrode active material, the binder, the conductive agent, and the additive.
17. The production method according to claim 15, wherein the mass percentage of the pole piece auxiliary agent represented by the formula III is 1 to 7% based on the total mass of the positive electrode active material, the binder, the conductive agent, and the additive.
18. The manufacturing method of claim 15, wherein the mass of the pole piece aid represented by formula III added is greater than the mass of the pole piece aid represented by formula I and less than ten times the mass of the pole piece aid represented by formula I.
19. The method of manufacturing of claim 11, wherein providing the first slurry comprises:
mixing and stirring the binder and the solvent at the stirring speed of 10-40rpm for 300-400 minutes to prepare binder glue solution;
mixing and stirring the positive electrode active material, the conductive agent and the binder glue solution, wherein the stirring speed is 25-40rpm, and the stirring time is 300-450 minutes; and
And adding the solvent for the second time and stirring to obtain the first slurry, wherein the stirring speed is 35-40rpm, and the stirring time is 20-120 minutes.
20. The production method according to claim 11, wherein the stirring speed of stirring performed after the addition of the additive to the first slurry is 10 to 20rpm, and the stirring time is 10 to 30 minutes.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210448313.8A CN116995234A (en) | 2022-04-26 | 2022-04-26 | Positive electrode sheet, electrochemical device, electronic device, and method for manufacturing positive electrode sheet |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210448313.8A CN116995234A (en) | 2022-04-26 | 2022-04-26 | Positive electrode sheet, electrochemical device, electronic device, and method for manufacturing positive electrode sheet |
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| CN202210448313.8A Pending CN116995234A (en) | 2022-04-26 | 2022-04-26 | Positive electrode sheet, electrochemical device, electronic device, and method for manufacturing positive electrode sheet |
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| CN (1) | CN116995234A (en) |
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