Electricity storage body

Abstract

The invention relates to a power storage body. The present invention comprises: a negative electrode; a positive electrode including at least one positive electrode active material containing a lithium element; a separation layer disposed between the positive electrode and the negative electrode; and an electrolyte comprising positive ions and negative ions; and an outer package including a positive electrode, a negative electrode, a separation layer, and an electrolyte. The negative electrode has a reduction reaction, a first reaction in which the negative electrode is combined with the first conductive substrate material, and a second reaction in which the negative electrode adheres to the substrate in a metal state. The power supply with large capacity and long service life is realized, and the industrial value is huge.

Description

Technical Field

[0001] The present invention relates to an electricity storage body. Background Art

[0002] The industrialization of storage devices using lithium as reactive species (hereinafter referred to as positive ions) has made it possible to store electricity for small machines, electric vehicles, renewable energy generation, etc. As is known to all, the above devices are widely used as power sources in daily life and are indispensable. By effectively using storage devices, the types of portable electrical appliances can be increased, and increasing the usage time has been a requirement since the commercialization of storage devices.

[0003] In order to use it for a long time, it is necessary to achieve high energy density of the storage device. In order to achieve this, the traditional reaction mode of positive ions and compounds accompanied by electron transfer in the positive and negative electrodes has reached the expected limit. One of the technologies that helps to increase the capacity of the device is that the positive ions are deposited as metals (hereinafter referred to as active species metals) and attached to the collector foil, which is a negative electrode technology that does not use compound reactions. Using only a single metal for charging and discharging, the capacity can theoretically be increased by up to 3860mAh / g, which is about 10 times that of traditional graphite negative electrodes.

[0004] However, during the precipitation process of active metal species, needle-shaped products with high specific surface area are easily produced, and the resulting major problems such as reduced charge and discharge life still exist. Summary of the invention

[0005] The present invention is proposed based on the above-mentioned problems and provides a power storage body.

[0006] It is possible to maximize the utilization of active seed metals and provide a method for solving the problem of extending service life.

[0007] As a result of intensive studies, the inventors of the present invention have discovered that a substrate designed and manufactured using a certain carbon-based material has excellent electronic conductivity and exhibits effective adhesion to an active seed metal.

[0008] In addition, it was found that the life of repeated attachment / detachment of metal during charge / discharge was also improved. Specifically, materials that form alloys and intercalation compounds in chemical reactions are preferred, and among them, carbon-based materials are more preferred because they have small volume changes when chemically combined and high conductivity. By using it, the above problems can be solved and the present invention can be completed.

[0009] One aspect of the present invention provides a power storage body, which comprises: a negative electrode; a positive electrode having at least one positive electrode active material containing a lithium element; a separator disposed between the positive electrode and the negative electrode; an electrolyte containing positive ions and negative ions; a terminal for connecting the positive electrode and the negative electrode to an external power supply circuit; and an outer packaging body including the positive electrode, the negative electrode, the separator, the electrolyte and the terminal; the negative electrode comprises: at least two conductive substrates, one of which has a conductivity of 1×10 7 S / m or above; the lithium ions released from the positive electrode undergo a reduction reaction, which includes a first reaction of combining with a conductive substrate material and a second reaction of attaching to the substrate in a metallic state, and the first reaction and the second reaction occur separately or simultaneously.

[0010] In some embodiments, the conductive substrate of the negative electrode contains crystalline carbon; the crystalline carbon is selected from one or more of graphite, hard carbon and soft carbon; the conductive substrate is made using an aggregate of the crystalline carbon in particle form; the conductive substrate is the other of the two conductive substrates in the above-mentioned negative electrode.

[0011] In some embodiments, the lithium insertion discharge capacity of the crystalline carbon is 300 mAh / cm 3 above.

[0012] In the present invention, as the negative electrode reaction, the first reaction in which positive ions combine with the negative electrode substrate material placed on the collector, and the second reaction in which the positive ions attach to the substrate in a metallic state, the first reaction and the second reaction occur separately or simultaneously. Figure 7 As shown, the figure shows the behavior of the negative electrode when it changes from a chemical reaction to an adhesion reaction. In fact, the second reaction does not occur after the first reaction is fully completed.

[0013] After considering the details involved in this matter, it was found that it is best to define the following conditions: That is, in the first reaction and the second reaction, the second reaction starts after the first reaction reaches 50% or more of the end point capacity, which improves the reversibility of the attachment / desorption reaction, which is more advantageous.

[0014] Here, if Figure 8 As mentioned above, the end point capacity refers to the capacitance when the substrate material reacts with positive ions in a lithium reference electrode standard and the reaction is completed after reaching 0V.

[0015] The main object of the present invention is to improve the reversibility of the above-mentioned attachment / detachment and to increase the capacity.

[0016] Regarding high capacity, it is necessary to stably and evenly attach and accumulate active metals on the negative electrode as much as possible. First, in order to achieve high battery capacity density, it is necessary to provide sufficient attachment and accumulation space. For this reason, the negative substrate needs to be as thin as possible. Considering the ease of industrialization, it is preferred to use a binder as the negative electrode material to thinly coat and fix the powder particles, and then compress them into a high density.

[0017] <Negative electrode>

[0018] The negative electrode substrate material may be a binding material or the like on a metal current collector (eg, copper foil) and a carbon material fixed thereto.

[0019] Specifically, as the carbon material, all carbon materials such as amorphous carbon and high crystallinity carbon can be used. Typical examples of low crystalline carbon include soft carbon and hard carbon, and typical examples of high crystalline carbon include natural graphite, Kish graphite, pyrolytic carbon, mesophase pitch based carbon fiber, mesocarbon microbeads, mesophase pitches, and carbon materials formed by high temperature sintering such as petroleum or coal coke. Although the grain size is different, each type of carbon has a crystalline structure.

[0020] Carbon materials can be made into various materials by changing the starting materials and manufacturing methods. In particular, changes in crystallinity will change the true density and charge-discharge capacity, and the particle size distribution will also change depending on the pulverization method. You can select any negative electrode substrate by selecting the electrode filling property and crystallinity based on the true density and particle size distribution.

[0021] Among them, graphite has high capacity density in terms of charge and discharge capacity and filling properties, and natural graphite is preferred in terms of cost.

[0022] At the same time or before the second reaction (i.e., metal adhesion to the negative electrode reaction) described above, an interlayer compound reaction, which is the basic property of carbon materials, occurs, and the contacting metal becomes ions and is inserted into the interior of the carbon material. At this time, when the surface structure of the carbon material is a material with low crystallinity, the reaction rate increases.

[0023] Particularly preferred is natural graphite coated with low-crystalline carbon on the surface. The raw material of low-crystalline carbon is mainly organic matter, and relatively low molecular weight organic matter discharged from various industries such as petroleum, coal, and high molecular polymers is impregnated on the graphite surface and heat-treated in an inert gas to produce a coating.

[0024] The higher the single discharge capacity of the carbon material causing the first reaction, the higher the charge-discharge reversibility of the present invention. The discharge capacity per unit volume is preferably 250 mAh / cm 3 above.

[0025] When the graphite material suitable for the negative electrode substrate material is fixed as a substrate, it must be arranged in a manner that the collector is not exposed. In addition, as mentioned above, in order to increase the amount of attached active metal, the substrate layer should be as thin as possible. When the substrate material is placed on the collector, in order to fully exert the adhesion induction force, its amount is preferably 0.5 mg / cm 2 Above and 7.0mg / cm 2 In addition, the collector surface needs to be exposed as little as possible, and the substrate material is pressed under high pressure to minimize the pores between the carbon material particles. Therefore, the volume density needs to be specified, preferably 1.0 g / cm 3 More preferably, 1.6 g / cm 3 above.

[0026] In the present invention, by combining the positive electrode layer, the negative electrode layer, the separator, etc., it is possible to design a storage body of any size, shape, and capacity. When various storage and discharge characteristics are required, the reversibility and other characteristics of the negative electrode can be improved by appropriately combining the substrate material, the active metal, and the charge and discharge capacity.

[0027] In the initial charge capacity of the electricity storage body, the ratio of the second reaction electricity to the first reaction electricity is preferably 2 to 10. Too much active species metal shortens the life of the electricity storage body, and too much substrate material reduces the discharge capacity of the electricity storage body.

[0028] <Positive electrode>

[0029] The positive electrode 10 may be in a sheet form. The positive electrode 10 may include, for example, a positive electrode collector 11 and a positive electrode mixture layer 12. The positive electrode collector 11 may be an aluminum foil or the like. The positive electrode collector 11 may have a thickness of, for example, 10 μm or more and 50 μm or less.

[0030] The positive electrode mixture layer 12 is formed on the surface of the positive electrode current collector 11. The positive electrode mixture layer 12 may be formed on the front and back surfaces of the positive electrode current collector 11. The positive electrode mixture layer 12 may have a thickness of 10 μm to 200 μm. The positive electrode mixture layer 12 contains at least a positive electrode active material.

[0031] There is no particular limitation on the positive electrode active material. The positive electrode active material may be, for example, LiCoO2, LiMnO2, LiMn2O4, Li(Ni,Co,Mn)O2 (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc.), LiFePO4, etc. Composite oxides with a high Ni ratio are particularly suitable. In addition, one positive electrode active material may be used alone, or two or more positive electrode active materials may be used in combination.

[0032] Here, the material used as the current collector substrate of the positive and negative electrodes is a metal material with high electronic conductivity, and any material that does not react within the voltage range of the past lithium ion secondary battery can be used. Specifically, the negative electrode collector includes but is not limited to a foil made of copper, gold, nickel, copper alloy or a combination thereof. The positive electrode collector includes but is not limited to a foil made of aluminum, nickel or a combination thereof. In addition, as the negative electrode collector and the positive electrode collector, a substrate stack composed of the above substances can also be used.

[0033] The negative electrode substrate layer and the positive electrode mixed layer 12 may further include a binder and / or a conductive material. The conductive material may be, for example, carbon black. The content of the conductive material may be, for example, 1 part by mass or more and 10 parts by mass or less relative to 100 parts by mass of the positive electrode active material. The binder is not particularly limited, and may be, for example, PVDF. The content of the binder may be, for example, 1 part by mass or more and 10 parts by mass or less relative to 100 parts by mass of the positive electrode active material.

[0034] The polymer binder used for the electrode is polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-co-chlorotrifluoroeth ylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethy! The present invention can be selected from the group consisting of thyl cellulose, cyanoethyl sucrose, pullulan, and carboxyl methylcellulose, or a mixture of two or more thereof, without particular limitation.

[0035] <Isolation Layer>

[0036] The separator must prevent the contact between the positive and negative electrodes and ensure that positive ions can be conducted between the positive and negative electrodes. For example, in the case of a liquid electrolyte, a porous polymer film having fine pores impregnated with a liquid is preferred. The separator may have a thickness of, for example, 5 μm or more and 50 μm or less. The porous polymer film may be made of polyolefin.

[0037] As the polyolefin polymer film, any commonly used polyolefin porous substrate can be used. Specifically, high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene and other polyethylene, polypropylene, polybutene, polypentene and other polyolefin polymers can be used alone or in combination to form a film.

[0038] The additional layer can be used to impart functionality to the polymer film. In order to improve the mechanical strength and the safety of the power storage device in abnormal mode, one or more insulating and / or electronically conductive isolation layers are preferably laminated on at least one side of the polymer film.

[0039] Organic and inorganic fillers can be used for the electrically insulating separator layer.

[0040] Inorganic fillers and the like may be used for the electron conductive isolation layer.

[0041] The above fillers can be used in porous coatings containing polymer binders.

[0042] The polymer binder includes one or a mixture of two or more of polyvinylidene fluoride (PVDF), hexafluoropropylene (HFP), polyvinylidene fluoride-co-chlorotrifluoroethylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, polyethylene-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate-butyrate (, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, and polyimide.

[0043] Here, there is no particular limitation on the inorganic filler as long as it is electrochemically stable. That is, as long as the inorganic filler is within the operating voltage range of the applied power storage body (for example, based on Li / Li + There is no particular restriction as long as no oxidation and / or reduction reaction occurs within the range of 0 to 5 V. In particular, when inorganic particles with a high dielectric constant are used as inorganic fillers, it helps to increase the degree of dissociation of positive ions of the electrolyte salt in the electrolyte, thereby improving the ionic conductivity of the electrolyte.

[0044] The filler layer coated on the above polymer film can be fixed by heat pressing.

[0045] The polymer film may be selected from one or a mixture of two or more of polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, and polynaphthalene other than polyolefin.

[0046] <Electrolytes>

[0047] In the present invention, the electrolyte may be in liquid or other forms. In the case of a liquid, it may contain an organic solvent and an organic and / or inorganic electrolyte salt.

[0048] The organic solvent must be liquid at the ambient temperature when the battery is used, and must have salt solubility and chemical and electrochemical stability with the positive and negative electrodes.

[0049] The organic solvent used in the conventional liquid electrolyte is not particularly limited, and cyclic carbonate, linear carbonate, lactone, ether, ester or ketone may be used.

[0050] Examples of the above-mentioned cyclic carbonates include: ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. Examples of the above-mentioned linear carbonates include: diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), etc. Examples of the above-mentioned lactones include: γ-butyrolactone (GBL). Examples of the above-mentioned ethers include: dibutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, etc. Examples of the above-mentioned esters include: methyl acetate, ethyl acetate, methyl propionate, methyl pivalate, etc. Examples of the above-mentioned ketones include: poly (vinyl methyl ketone). These non-aqueous solvents can be used alone or in mixtures of two or more.

[0051] In the liquid electrolyte, the electrolyte salt is compatible with the organic solvent at least at a ratio above the saturation concentration (below the crystallization concentration), and the reversibility of the attachment / detachment of the active metal is preferably high. The salt concentration is preferably 4 mol / L or more, more preferably 6 mol / L or more.

[0052] The electrolyte salt can be a conventional liquid electrolyte without any particular limitation. For example, the cation is the positive ion in the present invention and can also include a small amount of other types of cations. The anion can be a conventional electrolyte salt for non-aqueous electrolyte without any particular limitation. For example, the anion containing F - , Cl - Br - ,I - 、NO3 - 、N(CN)2 - 、BF4 - 、ClO4 - PF6 - 、(CF3)2PF4 - 、(CF3)3PF3 - 、(CF3)4PF2 - 、(CF3)5PF - 、(CF3)6P - CF3SO3 - CF3CF2SO3 - 、(CF3SO2)2N - 、(FSO2)2N - CF3CF2(CF3)2CO- 、(CF3SO2)CH - 、(SF5)3C - 、(CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - 、CH3CO2 - 、SCN - 、(CF3CF2SO2)2N - and (FSO2)2N - Salts of ions either alone or in combination.

[0053] The liquid electrolyte can be injected at an appropriate stage in the production process of the electricity storage body of the present invention, depending on the production process and the physical properties required for the final product. For example, it can be injected before assembling the electricity storage body or at the final stage of assembling the electricity storage body.

[0054] The external shape of the power storage body of the present invention including such an electrode assembly is not particularly limited, and may be cylindrical, square, bag-shaped, coin-shaped, or the like.

[0055] In the present invention, the terms “above” and “below” indicating a numerical range should be understood to include the endpoints of the numerical range.

[0056] Compared with the traditional power storage device that only uses the positive ion combination reaction, the present invention adds the metal adhesion reaction and obtains an unprecedented high capacity density power storage body. By optimizing the physical properties of the negative electrode substrate material and the electrode, the life characteristics that are particularly important in practical applications are significantly improved. The present invention realizes a large-capacity, long-life power supply and has great industrial value. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It shows the change of CE with cycles in Example 1-1;

[0058] Figure 2 The discharge capacity per unit volume and the average CE of 100 cycles of each material in Table 1 are shown;

[0059] Figure 3 It shows the relationship between electrode density and average CE in Table 2;

[0060] Figure 4 It shows the relationship between the area weight, discharge capacity ratio and average CE in Table 3;

[0061] Figure 5 It shows the relationship between the charge capacity ratio and the average CE in Table 4;

[0062] Figure 61 is a powder X-ray diffraction result showing the negative electrode substrate material of Example 1-1;

[0063] Figure 7 This is a conceptual diagram of the reactions of the first and second reactions;

[0064] Figure 8 It shows the end point capacity;

[0065] Fig. 9 It is a schematic diagram of the electricity storage body of the present invention.

[0066] Description of reference numerals:

[0067] 10 positive electrode; 11 positive electrode collector; 12 positive electrode mixed layer; 20 negative electrode substrate; 30 isolation layer; 50 outer packaging material; 51 positive electrode terminal; 52 negative electrode terminal. DETAILED DESCRIPTION

[0068] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present disclosure and its application or use. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0069] Example

[0070] <Manufacturing of Electricity Storage Body>

[0071] Example 1-1

[0072] (1) Manufacturing of positive electrode

[0073] Positive electrode active material 96 parts by weight of LiNi 0.85 Mn 0.075 Co 0.075 O2, 2.0 parts by weight of conductive material super P, and 2.0 parts by weight of binder polyvinylidene fluoride (PVDF) are added to the solvent N-methylpyrrolidone (NMP) to make a positive electrode active material slurry, which is coated on one surface of the aluminum collector, dried and rolled to a thickness of 79 μm, and the coating is punched into 100 mm squares to make a positive electrode. Aluminum terminals for connecting external power circuits, etc. are connected and fixed to the other uncoated surface.

[0074] (2) Manufacturing of negative electrode substrate

[0075] The negative electrode substrate material is prepared by attaching coal-based organic matter to the surface of natural graphite, and heat-treating it in an inert gas to obtain 94 parts by weight of carbon-coated natural graphite with an average particle size of 10 μm. 6.0 parts by weight of polyvinylidene fluoride (PVDF) is used as a binder and added to a solvent N-methylpyrrolidone (NMP) to prepare a negative electrode substrate slurry. The above negative electrode substrate slurry is applied to a conductive substrate copper foil (conductivity of 5.98×10 7 S / m) on a surface with a concentration of 2.5 mg / cm 2 After drying and rolling, the thickness becomes 15 μm, and the coating is punched into 102 mm square to make the negative electrode substrate. At this time, the electrode density of the negative electrode substrate layer is 1.67 g / cm 3 A nickel terminal for connecting an external power circuit, etc. is connected and fixed to another uncoated surface.

[0076] (3) Assembly

[0077] The negative electrode substrate, the separator, and the positive electrode were stacked in this order to form an electrode group. The separator was a polyethylene porous film (thickness 12 μm).

[0078] The electrode group is stored in the outer package, the electrolyte is injected into the outer package, the following components are used as electrolyte, and the outer package is sealed. The battery assembly is completed according to the above steps.

[0079] <Electrolyte salt composition> Positive ion: Positive ion in the present invention Negative ion: (FSO2)2N-

[0080] <Solvent>: Ethylene glycol dimethyl ether

[0081] <Salt concentration>: 6 mol / 1 liter of solvent

[0082] (Initial charge / discharge)

[0083] The constant current charge is performed at 0.1C until the battery reaches 4.25V, and after reaching 4.25V, the charge is continued until the current value reaches 0.05C, and then terminated. That is, under the above conditions, positive ions are released from the positive electrode, and a chemical reaction with the negative electrode substrate material occurs. In addition, the positive ions are reduced and deposited as metal on the substrate material at the same time or individually, so that the storage body reaches a fully charged state. If you want to confirm the state of the negative electrode reaction, you can stop charging at any voltage, disassemble the storage body in an inert gas, and observe the negative electrode for confirmation.

[0084] After the storage body is fully charged, it is discharged at a constant current of 0.2C until it reaches 2.5V, and then terminated. The discharge capacity obtained at this time is taken as the initial discharge capacity, which is 562mAh.

[0085] Example 2

[0086] As the negative electrode substrate material, coal-based coke was heat-treated at 3000°C, and coke-based artificial graphite with an average particle size of 11 μm was used. The electricity storage body was produced in the same manner as in Example 1-1 except that it was rolled under the same pressure. Thereafter, initial charge and discharge were performed to obtain the capacity.

[0087] Example 3

[0088] As the negative electrode substrate material, MCMB (mesophase carbon microbeads) were heat treated at 3000°C, and MCMB (mesophase carbon microbeads) with an average particle size of 15 μm were used. The storage body was prepared in the same manner as in Example 1-1 except that the MCMB was rolled under the same pressure. After that, initial charge and discharge were performed to obtain the capacity.

[0089] Example 4

[0090] As the negative electrode substrate material, hard carbon was heat-treated at 3000°C and hard carbon with an average particle size of 15 μm was used. The electricity storage body was prepared in the same manner as in Example 1-1 except that the rolling was performed under the same pressure. Thereafter, initial charge and discharge were performed to obtain the capacity.

[0091] Comparative Example 1

[0092] As the negative electrode substrate material, acetylene black was heat-treated at 3000°C, and hard carbon with an average particle size of 1 μm was used. The electricity storage body was prepared in the same manner as in Example 1-1 except that the rolling was performed under the same pressure. Thereafter, initial charge and discharge were performed to obtain the capacity.

[0093] (Charge and discharge capacity measurement of negative electrode substrate material)

[0094] After the negative electrode substrates of Examples 1 to 4 and Comparative Example 1 were punched into a diameter of 15.5 mm, the negative electrode substrate, the separator, and the lithium with a thickness of 100 μm punched into a diameter of 16 mm were laminated and encapsulated in a button cell injected with an electrolyte to prepare a test cell. The same separator and electrolyte as in Example 1 were used.

[0095] The button cell was charged to 0.0 V at a constant current of 0.1 C, and then continued to be charged until the current value reached 0.05 C, and then discharged at a constant current of 0.1 C until the discharge reached 1.5 V. The charge capacity and discharge capacity (insertion reaction capacity) obtained at this time were measured.

[0096] In addition, the electrode density of each negative electrode substrate was measured. The discharge capacity per unit volume was calculated from the above discharge capacity and electrode density. The results are shown in Table 1.

[0097] (Substrate material crystallinity index measurement)

[0098] The crystallinity index d002 of the negative electrode substrate materials of Examples 1 to 4 and Comparative Example 1 was measured by powder X-ray diffraction. The results are shown in Table 1. The powder X-ray diffraction results of the negative electrode substrate material of Example 1-1 are shown in Table 1. Figure 6 .

[0099] (Battery charge and discharge reversibility evaluation-1)

[0100] The power storage bodies of Examples 1 to 4 and Comparative Example 1 were connected to a control power supply, and the power storage bodies were charged at a constant current of 0.1C until reaching 4.25V. After reaching 4.25V, charging was continued until the current value reached 0.05C, and then discharged at a constant current of 0.5C, and continued to discharge until 2.5V was regarded as one cycle. This was continued until 100 cycles, and the ratio of discharge capacity to charge capacity (CE) of each cycle was determined, and the average value of all cycles was determined, as shown in Table 1.

[0101] CE is an indicator of how effectively the charge capacity of each cycle is utilized during discharge. The average value of 100 cycles is an indicator of total capacity utilization. The higher the CE, the higher the charge and discharge reversibility.

[0102] As an example, Figure 1 The change of CE with cycles in Example 1-1 is shown.

[0103] According to the results in Table 1, each carbon material shows an electrode density and a unit volume discharge capacity based on its own properties. The unit volume discharge capacity of each material and the average CE of 100 cycles are plotted in Figure 2 middle.

[0104] The results show that the higher the discharge capacity per unit volume, the higher the average CE. 3 Above is good, 350mAh / cm 3 The above is better.

[0105] Table 1:

[0106]

[0107] Example 1-2

[0108] In addition to pressing, the electrode density of the negative electrode substrate is 1.87g / cm 3 A power storage body was produced in the same manner as in Example 1-1 except for the above.

[0109] Examples 1-3

[0110] In addition to pressing, the electrode density of the negative electrode substrate is 1.94g / cm 3 A power storage body was produced in the same manner as in Example 1-1 except for the above.

[0111] Examples 1-4

[0112] In addition to pressing, the electrode density of the negative electrode substrate is 2.01g / cm 3 A power storage body was produced in the same manner as in Example 1-1 except for the above.

[0113] Comparative Example 2

[0114] In addition to pressing the negative electrode substrate to a density of 1.5 g / cm 3 A power storage body was produced in the same manner as in Example 1-1 except for the above.

[0115] Comparative Example 3

[0116] In addition to pressing, the electrode density of the negative electrode substrate is 1.55g / cm 3 A power storage body was produced in the same manner as in Example 1-1 except for the above.

[0117] (Evaluation of the reversibility of battery charge and discharge-2)

[0118] The charge / discharge reversibility evaluation was carried out in the same manner as above. The results are shown in Table 2 and Figure 3 shown.

[0119] Depend on Figure 3 The results show that 1.55g / cm 3 The above electrode density is highly practical and performs well.

[0120] (Porosity of negative electrode substrate)

[0121] The porosity was calculated from the electrode density of the negative electrode substrate. The results are shown in Table 2. Good performance was obtained when the porosity was 30% or less.

[0122] (Determination of the second reaction starting capacity ratio)

[0123] The negative electrode substrate was punched into a diameter of 15.5 mm, and the negative electrode substrate, separator and lithium with a thickness of 100 μm punched into a diameter of 16 mm were laminated and packaged in a button cell injected with electrolyte to prepare a test cell. The same separator and electrolyte as in Example 1 were used.

[0124] The button battery was charged to 0.0V at a constant current of 0.1C, and after reaching 0.0V, the battery was continuously charged until the current value reached 0.05C, and the total charge capacity was calculated. The second reaction start capacity ratio was obtained by dividing the capacity at 0.0V by the total charge capacity. When the second reaction start capacity ratio was 50% or higher, the characteristics were good.

[0125] Table 2:

[0126]

[0127] Examples 1-5

[0128] Except for the negative electrode substrate, the area weight is 1.5 mg / cm 2 A power storage body was produced in the same manner as in Example 1-1 except for the above.

[0129] Examples 1-6

[0130] Except for the negative electrode substrate, the area weight is 3.5 mg / cm 2 A power storage body was produced in the same manner as in Example 1-1 except for the above.

[0131] Examples 1-7

[0132] Except for the negative electrode substrate, the area weight is 5.5 mg / cm 2 A power storage body was produced in the same manner as in Example 1-1 except for the above.

[0133] Comparative Example 4

[0134] Except for the negative electrode substrate, the area weight is 1.0 mg / cm 2 A power storage body was produced in the same manner as in Example 1-1 except for the above.

[0135] Comparative Example 5

[0136] Except for the negative electrode substrate, the area weight is 7.5 mg / cm 2 A power storage body was produced in the same manner as in Example 1-1 except for the above.

[0137] (Battery charge and discharge reversibility evaluation-3)

[0138] The charge / discharge reversibility evaluation was performed in the same manner as above. The ratio of the initial discharge capacity of Example 1-1, each example and the comparative example was determined. The results are shown in Tables 3 and Figure 4 shown.

[0139] Figure 4 The results show that when the area weight is 1.25-7.0 mg / cm 2 When the discharge capacity and charge-discharge reversibility are within the range of , the discharge capacity and charge-discharge reversibility can be achieved simultaneously.

[0140] Table 3

[0141]

[0142] (Battery charge and discharge reversibility evaluation-4)

[0143] For Examples 1-1, 1-5, 1-6 and Comparative Examples 4 and 5, the ratio of the attached charge to the combined charge in the initial charge capacity was determined. Specifically, the charge capacity per unit weight of the substrate material obtained in the charge and discharge capacity measurement of the substrate material was multiplied by the weight of the substrate material to obtain the combined charge capacity, that is, the charge capacity obtained by the initial charge and discharge of the storage body minus the charge capacity attached as metal. Determine the ratio of the attached charge capacity to the combined charge capacity (Table 4). The relationship between this ratio and the average CE of 100 cycles is as follows: Figure 5 shown.

[0144] Figure 5 The results in show that the ratio of the adhesion charge capacity to the combined charge capacity is preferably in the range of 2-10.

[0145] Table 4:

[0146]

[0147] Compared with the traditional power storage device that only uses the positive ion combination reaction, the present invention adds the metal adhesion reaction and obtains an unprecedented high capacity density power storage body. By optimizing the physical properties of the negative electrode substrate material and the electrode, the life characteristics that are particularly important in practical applications are significantly improved. The present invention realizes a large-capacity, long-life power supply and has great industrial value.

[0148] So far, the embodiments of the present disclosure have been described in detail. In order to avoid obscuring the concept of the present disclosure, some details known in the art are not described. Based on the above description, those skilled in the art can fully understand how to implement the technical solutions disclosed herein.

[0149] Although some specific embodiments of the present disclosure have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present disclosure. It should be understood by those skilled in the art that the above embodiments may be modified or some technical features may be replaced by equivalents without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims

1. An electric storage body, comprising: negative electrode; A positive electrode having at least one positive electrode active material containing a lithium-containing element; A separation layer, disposed between the positive electrode and the negative electrode; electrolytes, which contain positive and negative ions; terminals for connecting the positive and negative terminals to an external power circuit; and An outer packaging body including the positive electrode, the negative electrode, the separator, the electrolyte and the terminal; The negative electrode include: At least two conductive substrates; lithium ions released from the positive electrode undergo a reduction reaction, which includes a first reaction of combining with the conductive substrate material and a second reaction of attaching to the substrate in a metallic state, wherein the first reaction and the second reaction occur separately or simultaneously.

2. The electricity storage body according to claim 1, in, After the first reaction reaches more than 50% of the endpoint capacity of the first reaction, the second reaction begins to occur; The end point capacity is the capacity when the conductive substrate material reacts with lithium positive ions to reach 0V.

3. The electricity storage body according to claim 1 or 2, in, The conductive substrate of the negative electrode contains crystalline carbon; The crystalline carbon is selected from one or more of graphite, hard carbon and soft carbon; A conductive substrate is produced using the aggregate of the crystalline carbon in a particle form.

4. The electricity storage body according to claim 3, in, The conductive substrate containing crystalline carbon has a 3 The above unit volume weight.

5. The electricity storage body according to claim 3, in, The conductive substrate containing crystalline carbon has a 0.5 mg / cm 2 Above and 7.0mg / cm 2 The following weight per unit area.

6. The electricity storage body according to claim 3, in, The lithium insertion discharge capacity of the crystalline carbon is 300 mAh / cm 3 above.

7. The electricity storage body according to claim 1 or 2, in, The ratio of the second reaction electric quantity to the first reaction electric quantity in the initial charge capacity of the electric storage body is 2-10.

8. The electricity storage body according to claim 3, in, The crystalline carbon includes graphite.

9. The electricity storage body according to claim 3, in, The crystalline carbon includes a component having a lower crystallinity than graphite.

10. The electricity storage body according to claim 1, in, The electrolyte is a liquid electrolyte, and the lithium salt concentration in the liquid electrolyte is greater than 1.5 mol / L; the conductivity of one of the at least two conductive substrates at 20° C. is 1×10 7 S / m and above.

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