CN115602942B - Negative pole piece, secondary battery and electric equipment - Google Patents

Abstract

The invention discloses a negative electrode sheet, a secondary battery and an electrical device. The negative electrode sheet includes a negative electrode collector and a negative electrode active layer arranged on at least one side of the negative electrode collector. The negative electrode active layer includes a conductive Agent, binding agent and comb polymer, the structural formula of the comb polymer is as shown in formula I:

Formula I; wherein, n≥10000; R is selected from substituted or unsubstituted naphthyl, substituted or unsubstituted biphenyl, substituted or unsubstituted anthracenyl or substituted or unsubstituted phenanthrenyl. The negative pole piece prepared by the present invention with the comb-shaped polymer represented by the structure of formula I, the conductive agent and the binder has high coulombic efficiency, cycle stability and energy density.

Description

Negative electrode sheet, secondary battery and electrical equipment

technical field

The invention relates to the technical field of energy storage, in particular to a negative pole piece, a secondary battery and electrical equipment.

Background technique

Energy storage technology is the core technology that determines the national energy security and sustainable development strategy. The current traditional lithium-ion battery energy storage technology is facing severe problems such as limited material reserves, high prices, serious pollution, and limited improvement in energy density. At present, the optimization of lithium-ion batteries mainly focuses on improving the voltage and capacity of the battery. However, the actual lithium storage capacity of the transition metal layered compound positive electrode and graphite negative electrode of traditional lithium-ion batteries is very close to the theoretical value. What can be done at present is to optimize the electrode structure and modify the components of the battery, so there is limited room for improvement. Many researchers believe that improvements to lithium-ion batteries could increase energy density by up to another 30 percent. The main metal elements used in lithium-ion batteries include lithium, cobalt, nickel and copper, but the limited resources and uneven distribution of reserves lead to the high cost of lithium-ion energy storage, which largely limits the use of lithium-ion batteries in large-scale energy storage and electric vehicles. Large-scale applications in the automotive field. At the same time, the mining and processing of transition metals lead to serious environmental pollution. All these challenges make it increasingly urgent to develop next-generation electrode materials with high energy density, low cost, and environmental protection. The specific research and development plan released by the New Energy Industrial Technology Development Organization (NEDO), a national research institution in Japan, is: 300 Wh/kg in 2025, 400 Wh/kg in 2030, and 500 Wh/kg in 2035. The Joint Center for Energy Storage Research (JCESR), funded by the U.S. Department of Energy (DOE), has released the "5-5-5" plan, starting in 2013 to develop energy density to five times within five years and reduce the price to 1/2. 5 batteries.

Organic materials have become popular candidates for next-generation energy storage technology due to their advantages such as abundant resources, low cost, safety, and low pollution. The organic electrodes reported so far are mainly divided into seven categories: conjugated hydrocarbons, conjugated amines, conjugated thioethers, organic sulfides, thioethers, nitroxyl radicals, and conjugated carbonyls. Most of the reported redox potentials of organic molecules are distributed in 1.5-3.5 V vs Li/Li ⁺ , and are generally used as positive electrode materials for batteries, and the matching negative electrodes are still traditional graphite or metal lithium. Although such a combination avoids the use of transition metal positive electrodes and reduces the cost of the battery, the lithium dendrites generated by the graphite negative electrode or the long-term cycle of lithium metal will eventually lead to a short circuit of the battery, which brings great safety to the operation of the battery. Hidden danger. Therefore, the development of organic anode materials with high energy density and low redox potential to replace the criticized graphite anode will have a high industrial application prospect.

In order to develop organic negative electrode materials with low redox potential, researchers have screened many organic molecules. Aromatic hydrocarbons (such as naphthalene, biphenyl, phenanthrene, etc.) represent another class of potential organic negative electrode materials, but aromatic carbon Hydrogen compounds and aromatic radicals are easily soluble in common organic solvents, and are often used as negative electrodes for flow batteries. However, the specific capacity of this liquid anode is much lower than that of the solid-state electrode of lithium-ion batteries, so it is difficult to apply it to high-energy-density energy storage systems.

Contents of the invention

The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the first aspect of the present invention proposes a negative pole piece, which can effectively improve Coulombic efficiency, cycle stability and energy density.

The second aspect of the present invention also provides a secondary battery.

The third aspect of the present invention also provides an electric device.

According to the negative electrode sheet of the embodiment of the first aspect of the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer arranged on at least one side of the negative electrode current collector, the negative electrode active layer includes a conductive agent, a binder Agent and comb polymer, the structural formula of the comb polymer is as shown in formula I:

Formula I;

Among them, n≥10000;

R is selected from substituted or unsubstituted naphthyl, substituted or unsubstituted biphenyl, substituted or unsubstituted anthracenyl or substituted or unsubstituted phenanthrenyl.

The negative electrode sheet according to the embodiment of the present invention has at least the following beneficial effects:

The negative pole sheet prepared by the present invention with the comb-shaped polymer represented by the structure of formula I, the conductive agent and the binder has high coulombic efficiency, capacity retention rate and energy density. This is because the comb polymer has a large molecular weight and a greatly reduced solubility in the electrolyte solution, and the anion radicals generated after being reduced mainly exist in the solid phase, so there is almost no shuttle effect.

According to some embodiments of the present invention, R is selected from naphthyl, biphenyl, anthracenyl or phenanthrenyl.

According to some embodiments of the present invention, the comb polymer is one of the following structural formulas:

.

According to some embodiments of the present invention, the number average molecular weight of the comb polymer is ≥10000.

According to some embodiments of the present invention, the preparation method of the comb polymer comprises the following steps:

Under the conditions of an inert atmosphere, toluene, n-butyllithium and n-hexane, add vinyl aromatic compound monomers for polymerization, and then add a polymerization inhibitor to stop the polymerization to obtain a comb polymer.

According to some embodiments of the present invention, the comb polymer accounts for 80%-99% of the total mass of the negative active layer.

According to some embodiments of the present invention, the conductive agent includes at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, metal powder and carbon fiber.

According to some embodiments of the present invention, the binder includes at least one of styrene-butadiene rubber or polyvinylidene fluoride.

According to some embodiments of the present invention, based on the total mass of the negative electrode active layer, the negative electrode active layer includes the following components calculated by mass percentage:

Comb polymer 80%~99%;

Conductive agent 0.05~15%;

Binder 0.05~15%.

According to some embodiments of the present application, the preparation method of the negative electrode sheet includes the following steps:

S1. Stir the comb polymer, the conductive agent and the first binder to obtain the negative electrode active layer

S2. The upper and lower surfaces of the negative electrode collector are coated by a double-layer coating method, and then dried, rolled, and cut to obtain the negative electrode sheet.

According to the second aspect of the present invention, an embodiment provides a secondary battery, which includes a positive electrode sheet, an electrolyte, a separator, and the above-mentioned negative electrode sheet.

According to some embodiments of the present invention, the separator is interposed between the positive pole piece and the negative pole piece, and the electrolyte is filled between the positive pole piece and the negative pole piece and wets the diaphragm.

According to some embodiments of the present invention, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. For example, the positive electrode current collector includes two opposite surfaces in its thickness direction, and the positive electrode active material layer is stacked on any one or both of the two surfaces of the positive electrode current collector.

According to some embodiments of the present invention, the positive pole piece includes a positive active material, and the positive active material can be selected from lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt Manganese oxide, lithium nickel cobalt aluminum oxide, lithium-containing phosphate of olivine structure, etc., but the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for lithium ion batteries can also be used . These positive electrode active materials may be used alone or in combination of two or more. Preferably, the positive electrode active material can be selected from LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM111), LiNi _0.5 Co _0.2 Mn _0.3 O ₂ ( One or more of NCM523), LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM622), LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811), LiNi _0.85 Co _0.15 Al _0.05 O ₂ , LiFePO ₄ , LiMnPO ₄ .

According to some embodiments of the present application, the positive electrode active material layer may further include a conductive agent to improve the conductivity of the positive electrode. The present application does not specifically limit the type of conductive agent, which can be selected according to actual needs. As an example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene or carbon nanofibers.

According to some embodiments of the present application, the positive electrode active material layer may further include a binder to firmly bind the positive electrode active material and an optional conductive agent on the positive electrode current collector. This application does not specifically limit the type of binder, which can be selected according to actual needs. As examples, the binder can be polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene-butadiene At least one of rubber (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA) or carboxymethyl chitosan (CMCS).

According to some embodiments of the present application, the positive current collector adopts conductive carbon sheet, metal foil, carbon-coated metal foil, porous metal plate or composite current collector, wherein the conductive carbon material of the conductive carbon sheet can be superconducting carbon, acetylene black, One or more of carbon black, ketjen black, carbon dots, carbon nanotubes, graphite, graphene or carbon nanofibers, the metal material of metal foil, carbon-coated metal foil and porous metal plate can be independently selected At least one of copper, aluminum, nickel and stainless steel. The composite current collector may be a composite current collector formed by compounding metal foil and polymer base film.

According to some embodiments of the present application, the separator can be a variety of materials suitable for secondary battery separators in the field, for example, including but not limited to polyethylene, polypropylene, polyvinylidene fluoride, aramid fiber, polyterephthalene At least one of ethylene glycol formate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fiber.

According to some embodiments of the present application, the electrolyte solution includes an organic solvent and an electrolyte sodium salt. For example, organic solvents include ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, methyl acetate, ethyl propionate, fluoroethylene carbonate, diethyl ether, One or more of diglyme, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, methyl tert-butyl ether; electrolyte sodium salts include sodium hexafluorophosphate, difluorosulfonyl One or more of sodium imide, sodium bistrifluoromethanesulfonylimide, sodium trifluoromethanesulfonate, sodium tetrafluoroborate, sodium difluorophosphate, sodium perchlorate, and sodium chloride.

The embodiment of the third aspect of the present application provides an electric device, where the electric device includes the above-mentioned secondary battery.

According to some embodiments of the present application, the electrical equipment includes a mobile phone, a computer, a wearable device, a mobile power supply, an electric vehicle, an energy storage device, and the like.

Definitions and General Terms

As used herein, "substituted or unsubstituted" means that a group may or may not be further substituted with one or more groups selected from the group consisting of: alkyl, alkenyl, alkynyl, aryl, halogen, haloalkyl , haloalkenyl, haloalkynyl, haloaryl, hydroxy, alkoxy, alkenyloxy, aryloxy, benzyloxy, haloalkoxy, haloalkenyloxy, haloaryloxy, Nitro, nitroalkyl, nitroalkenyl, nitroalkynyl, nitroaryl, nitroheterocyclyl, amino, alkylamino, dialkylamino, alkenylamino, alkynylamino, aryl Amino, diarylamino, phenylamino, diphenylamino, benzylamino, dibenzylamino, hydrazino, acyl, amido, diamido, acyloxy, heterocyclyl, heterocyclyloxy, Heterocyclylamino, halogenated heterocyclyl, carboxyl ester, carboxyl, carboxamide, mercapto, alkylthio, benzylthio, acylthio and phosphorus-containing groups.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and comprehensible from the description of the embodiments in conjunction with the following drawings, wherein:

Fig. 1 is the proton nuclear magnetic resonance spectrogram of the comb polymer prepared by embodiment 1;

Fig. 2 is the charge and discharge test diagram of the negative pole sheet prepared in embodiment 1;

FIG. 3 is a charge and discharge test chart of the negative electrode sheet prepared in Comparative Example 1. FIG.

Detailed ways

The following are specific examples of the present invention, and further describe the technical solutions of the present invention in conjunction with the examples, but the present invention is not limited to these examples.

The reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field unless otherwise specified.

Example 1

Embodiment 1 provides a kind of negative pole piece, and negative pole piece comprises negative electrode current collector and is arranged on the negative electrode active layer of one side of negative electrode current collector, and negative electrode active layer comprises conductive agent, binding agent and comb polymer, and comb polymer The structural formula is as shown in formula I:

Formula Ⅰ

The preparation method of comb polymer is as follows:

1. Rinse a 50 mL Schlenk bottle with dry nitrogen at room temperature, add 5 mL of toluene, and add 0.2 mL of n-BuLi in n-hexane (1.25 M) under nitrogen protection.

2. After stirring for 10 minutes, add 5 mL (0.65 M) of a toluene solution of 2-vinylnaphthalene, and stir and polymerize for 3 h under nitrogen protection. Excess methanol (20 mL) was added to stop the polymerization reaction, and the white poly(2-vinylnaphthalene) (formula I) formed by the polymerization was precipitated.

3. Filter the separated precipitate and dissolve it again in 10 mL of toluene, and stir until the precipitate is completely dissolved. Add excess methanol (20 mL) to precipitate poly(2-vinylnaphthalene). This step of purification process was repeated 1-3 times.

4. Dry and grind the separated precipitate and put it in the glove box for later use.

The prepared poly(2-vinylnaphthalene) is subjected to proton nuclear magnetic resonance spectrum testing, and the results are shown in Figure 1. The peak (Hb) in the range of 5-8ppm belongs to the hydrogen on the aromatic ring of naphthyl, and the peak in the range of 0-2ppm (Ha) belongs to the methylene hydrogen on the alkyl chain.

The preparation method of the negative electrode sheet is as follows:

S1. Dissolve the binder polyvinylidene fluoride (PVDF) in N-methylpyrrolidone, and make a uniform slurry with ground conductive carbon black and poly(2-vinylnaphthalene). The mass percentages of PVDF, conductive carbon black and poly(2-vinylnaphthalene) were 10%, 10% and 80%, respectively.

S2. Apply the above slurry evenly on the copper foil with a coater, dry it in a fume hood at room temperature, and then dry it completely in a blast drying oven at 60°C.

S3. Cut the dried electrode into a circle with a diameter of 14 mm with a trimmer, and place it in a drying oven for use.

Example 2

Embodiment 2 provides a kind of negative pole piece, and negative pole piece comprises negative electrode current collector and is arranged on the negative electrode active layer of one side of negative electrode current collector, and negative electrode active layer comprises conductive agent, binding agent and comb polymer, and comb polymer The structural formula is as shown in formula I:

Formula Ⅰ

The preparation method of comb polymer is as follows:

1. Rinse a 50 mL Schlenk bottle with dry nitrogen at room temperature, add 5 mL of toluene, and add 0.2 mL of n-BuLi in n-hexane (1.25 M) under nitrogen protection.

2. After stirring for 10 minutes, add 5 mL (0.65 M) of a toluene solution of 4-vinylbiphenyl, and stir and polymerize for 3 h under nitrogen protection. Excess methanol (20 mL) was added to stop the polymerization reaction, and the white poly(4-vinylbiphenyl) (formula Ⅰ) formed by the polymerization was precipitated.

3. Filter the separated precipitate and dissolve it again in 10 mL of toluene, and stir until the precipitate is completely dissolved. Add excess methanol (20 mL) to precipitate poly(2-vinylnaphthalene). This step of purification process was repeated 1-3 times.

4. Dry and grind the separated precipitate and put it in the glove box for later use.

The preparation method of the negative electrode sheet is as follows:

S1. Dissolve the binder polyvinylidene fluoride (PVDF) in N-methylpyrrolidone, and make a uniform slurry with ground conductive carbon black and poly(4-vinylbiphenyl). The mass percentages of PVDF, conductive carbon black and poly(4-vinylbiphenyl) were 10%, 10% and 80%, respectively.

S2. Apply the above slurry evenly on the copper foil with a coater, dry it in a fume hood at room temperature, and then dry it completely in a blast drying oven at 60°C.

S3. Cut the dried electrode into a circle with a diameter of 14 mm with a trimmer, and place it in a drying oven for use.

Example 3

Embodiment 3 provides a kind of negative pole piece, and negative pole piece comprises negative electrode current collector and is arranged on the negative electrode active layer of one side of negative electrode current collector, and negative electrode active layer comprises conductive agent, binding agent and comb polymer, and comb polymer The structural formula is as shown in formula I:

Formula Ⅰ

The preparation method of comb polymer is as follows:

1. Rinse a 50 mL Schlenk bottle with dry nitrogen at room temperature, add 5 mL of toluene, and add 0.2 mL of n-BuLi in n-hexane (1.25 M) under nitrogen protection.

2. After stirring for 10 minutes, add 5 mL (0.65 M) of a toluene solution of 2-vinylanthracene, and stir and polymerize for 3 h under nitrogen protection. Excess methanol (20 mL) was added to stop the polymerization reaction, and the white poly(2-vinyl anthracene) (formula I) formed by the polymerization was precipitated.

3. Filter the separated precipitate and dissolve it again in 10 mL of toluene, and stir until the precipitate is completely dissolved. Add excess methanol (20 mL) to precipitate poly(2-vinylnaphthalene). This step of purification process was repeated 1-3 times.

4. Dry and grind the separated precipitate and put it in the glove box for later use.

The preparation method of the negative electrode sheet is as follows:

S1. Dissolve the binder polyvinylidene fluoride (PVDF) in N-methylpyrrolidone, and make a uniform slurry with ground conductive carbon black and poly(2-vinyl anthracene). The mass percentages of PVDF, conductive carbon black and poly(2-vinylanthracene) were 10%, 10% and 80%, respectively.

S2. Apply the above slurry evenly on the copper foil with a coater, dry it in a fume hood at room temperature, and then dry it completely in a blast drying oven at 60°C.

S3. Cut the dried electrode into a circle with a diameter of 14 mm with a trimmer, and place it in a drying oven for use.

Comparative example 1

Comparative example 1 provides a kind of negative electrode sheet, and negative electrode sheet comprises negative electrode current collector and is arranged on the negative electrode active layer of negative electrode current collector one side, and negative electrode active layer comprises conductive agent, binding agent and 2-vinyl naphthalene, 2-ethylene The structural formula of base naphthalene is as follows:

The preparation method and content of the negative electrode sheet are the same as in Example 1.

performance testing

Preparation of secondary battery:

(1) Diaphragm: polypropylene film;

(2) Preparation of positive pole piece:

Mix the positive electrode active material lithium iron phosphate (LiFePO ₄ ), the conductive agent acetylene black, and the binder PVDF at a mass ratio of 96:2:2, add the solvent NMP, and stir until the system is uniform under the action of a vacuum mixer to obtain the positive electrode Slurry: The positive electrode slurry is uniformly coated on the positive electrode current collector aluminum foil, dried at room temperature, transferred to an oven for further drying, and then cold pressed and cut to obtain the positive electrode sheet.

(3) Preparation of electrolyte:

Mix ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an organic solvent, and then dissolve fully dried LiPF ₆ in the mixed In an organic solvent, prepare an electrolyte solution with a concentration of 0.5mol/L.

Wind the negative pole piece, positive pole piece, and separator prepared in the above-mentioned Examples 1-3 and Comparative Example 1 to obtain a winding core, and package the winding core to obtain a dry cell, and then inject liquid and form the dry cell after baking. , two seals, and sorting to obtain the secondary battery, and finally the secondary battery is tested with an electrochemical workstation.

Electrochemical performance test:

Coulombic efficiency: The test voltage range is 2.0-3.8 V. The test steps and conditions are 1. Stand still for 2 hours; 2. Charge at 0.2C to a voltage ≥ 3.8V; 3. Discharge at 0.5C to a voltage ≤ 2.0 V; 4. Cycle charge and discharge 100 times at a rate of 0.5C, and get each cycle After calculating the average Coulombic efficiency of 100 cycles, the test results are shown in Table 1.

Capacity retention: The test voltage range is 2.0-3.8 V. The test steps and conditions are 1. Stand still for 2 hours; 2. Charge at 0.2C to a voltage ≥ 3.8V; 3. Discharge at 0.5C to a voltage ≤ 2.0 V; 4. Cycle charge and discharge 100 times at a rate of 0.5C, the 100th cycle The ratio of the discharge capacity to the initial discharge capacity was used as the capacity retention rate.

Energy density: The calculation of energy density only considers the quality of the positive and negative active materials, and the voltage and capacity use the average discharge voltage and the average capacity of the first 100 cycles, respectively. Record the data in Table 1.

The data of table 1 embodiment 1～3 and comparative example 1

the Coulombic efficiency% Capacity retention% Energy density (Wh/kg) Example 1 97.6 91.3 221.9 Example 2 98.8 90.6 208.7 Example 3 97.5 94.6 232.4 Comparative example 1 83.2 40.4 143.6

Fig. 2 is a half-cell charge test diagram of the negative electrode sheet prepared in Example 1. From Fig. 2, the coulombic efficiency of the first discharge is not high, because the generation of SEI is accompanied by the first discharge process. Afterwards, the cycle Coulombic efficiency increased to and stabilized above 95%, indicating that the generated SEI was very stable, and the dissolution and shuttling effects of electrode materials were basically effectively suppressed.

Figure 3 is a half-cell charge and discharge test diagram of the negative electrode sheet prepared in Comparative Example 1. From Figure 3, the generation of SEI is also accompanied by the first discharge process, but due to the large solubility of ethyl naphthalene, the generated SEI is not unstable. The voltage could not reach the charging cut-off voltage during the first charging process, which indicated that the dissolution of small molecules of ethylnaphthalene caused a severe shuttle effect, resulting in a significant decrease in Coulombic efficiency.

The above has been described in detail in conjunction with the embodiments of the present invention, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those of ordinary skill in the art without departing from the gist of the present invention.

Claims (9)

1. The negative pole piece is characterized by comprising a negative pole current collector and a negative pole active layer arranged on at least one side of the negative pole current collector, wherein the negative pole active layer comprises a conductive agent, a binder and a comb-shaped polymer, and the comb-shaped polymer is an active substance; the structural formula of the comb polymer is shown as the formula I:

formula I;

wherein n is more than or equal to 10000;

r is selected from naphthyl, biphenyl, anthryl or phenanthryl.

2. The negative electrode plate as claimed in claim 1, wherein the comb polymer is one of the following structural formulas:

。

3. the negative electrode plate as claimed in claim 1, wherein the comb-shaped polymer has a number average molecular weight of 10000 or more.

4. The negative electrode plate as claimed in claim 1, wherein the comb-shaped polymer accounts for 80-99% of the total mass of the negative electrode active layer.

5. The negative electrode sheet according to claim 1, wherein the conductive agent comprises at least one of conductive carbon black, acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, metal powder, and carbon fiber.

6. The negative electrode tab of claim 1, wherein the binder comprises at least one of styrene butadiene rubber or polyvinylidene fluoride.

7. The negative electrode sheet according to claim 1, wherein the negative electrode active layer comprises the following components in percentage by mass, based on the total mass of the negative electrode active layer:

80% -99% of comb-type polymer;

0.05 to 15 percent of conductive agent;

0.05 to 15 percent of binder.

8. A secondary battery comprising a positive electrode sheet, an electrolyte, a separator and the negative electrode sheet defined in any one of claims 1~7.

9. An electric device comprising the secondary battery according to claim 8.

Images