CN1331848A - Microporous solid electrolytes and methods for preparing them - Google Patents

Abstract

The present invention relates to a solid electrolyte having a good conductivity to lithium ion by allowing the liquid components and lithium salts to be absorbed into the electrolyte film containing an absorbent added at the time of its preparation and having a porosity, a process for preparing the same and a rechargeable lithium cell using the same as an electrolyte. As the absorbent, inorganic materials having not more than 40 mu m of particle size can be used. As the polymer binder, any binder of whom solubility against the liquid electrolyte is small can be used. A wet process can introduce the porous structure of the electrolyte film. The solid electrolyte according to the present invention has the ionic conductivity of more than approximately 1 to 3 x 10<-3> S/cm at room temperature and low reactivity to lithium metal. The cell is fabricated from the solid electrolyte together with electrodes by lamination or pressing methods and, the liquid electrolyte, which is decomposed by moisture, is introduced to a cell just before packaging. Therefore, the solid electrolyte according to the present invention is not affected by the humidity and temperature conditions during the manufacturing of the electrolyte film. In addition, the solid electrolyte according to the present invention has high thermal, mechanical and electrochemical stability, and thus is suitable as an electrolyte for rechargeable lithium cells.

Description

Microporous solid electrolyte and preparation method thereof

technical field

The present invention relates to an electrolyte membrane for a rechargeable battery. More specifically, by introducing liquid components and lithium salts (collectively referred to as "liquid electrolyte" hereinafter) into an electrolyte membrane having a microporous structure and containing an adsorbent, during repeated charging and discharging of a rechargeable battery, the Provide channels for the flow of ions between the anode and the

An electrochemical cell consists of three important parts, the cathode, the anode, and the electrolyte. Examples of said anode materials are mixtures to which lithium metal or lithium ions can be added, preferably carbon and polymeric materials. Examples of the cathode material are materials to which lithium ions can be added, for example, oxide or polymer materials such as lithium cobalt oxide (Li _x CoO ₂ ), lithium nickel oxide (Li _x NiO ₂ ), lithium Nickel cobalt oxide (Li _x Ni _y Co _1-y O ₂ ), spinel lithium manganese oxide (Li _x Mn ₂ O ₄ ), and manganese dioxide (M _n O ₂ ). Introduction of a liquid electrolyte into the electrolyte membrane results in the formation of an ionically conductive matrix.

Background technique

Electrochemical cells using polymer electrolytes have the following advantages over cells using liquid electrolytes: (1) they are not prone to leakage; (2) they have excellent electrochemical stability, a property that allows them to manufacture different types of batteries; and (3) they facilitate automatic control of the manufacturing process.

Because the polar heterogeneous atoms contained in polymers such as polyoxyethylene can electrically interact with metal ions, so that the polymers have metal ion conductivity, the research on ion-conducting polymers (ie, polymer electrolytes) has been researched. Actively develop. However, since pure polymers such as polyoxyethylene have very low ionic conductivity (approximately 10 ^-8 S/cm) at room temperature, they have the disadvantage of achieving the approximately 10 ^-4 S/cm required for electrochemical cells The ionic conductivity can only work at a temperature of about 100 ℃. For this reason, research on polymer electrolytes has mainly focused on improving electrical conductivity.

It has been found that the conduction of ions in polymer electrolytes requires the transfer of polymer chains, so attempts are made to increase the conductivity of ions by increasing the fluidity of polymer chains. Blonsky et al. proposed a method of making electrolytes with increased conductivity to 10 ^-5 S/cm by introducing phosphazene linkages to the polymer backbone (J.Am.Chem.Soc., 106, 6854 (1984 )). However, said electrolyte still has low electrical conductivity and poor mechanical strength.

On the other hand, in order to reduce the crystallinity of polymers, attempts have been made by changing the structure of polymers or adding inorganic materials to polymers. However, pure polymer electrolytes (without liquid electrolytes) composed of polymers and metal salts still do not possess sufficient electrical conductivity.

In contrast, gel-type electrolytes disclosed in U.S. Patent No. 5,219,679 contain liquid electrolytes on their polymer backbones, demonstrating electrical conductivity in the vicinity of liquid electrolytes, while their mechanical properties have properties of polymers, which are important for rechargeable batteries. commercialization is possible. That is to say, the battery of the said patent does not require the activation process of adding a liquid electrolyte separately, but combines a certain amount of liquid electrolyte. However, the electrolyte of U.S. Patent 5,219,679 still has some problems because the contained polymers (such as polyacrylonitrile) react with lithium metal, so that the reaction products of the electrolyte and the lithium electrode will gradually accumulate during storage and use of the battery, This leads to a continuous increase in interfacial resistance.

Meanwhile, Scrosati et al. prepared a gel-type polymer electrolyte using polymethylmethacrylate having low reactivity with lithium metal (Electrochim. Acta, 140, 991 (1995)). The electrolyte using polymethyl methacrylate as a polymer component has low reactivity on the lithium surface, and thus has the advantage that the phenomenon of resistance increase at the electrode surface during storage is suppressed. However, its disadvantage is that the mechanical strength of the electrolyte is low, so the content of the polymer should be increased to make it strong enough to form a membrane, which in turn reduces the conductivity to 10 ⁻⁴ S/cm. In addition, since gel-type electrolytes contain a large amount of liquid components, evaporation of the liquid components inevitably occurs on the surface of the electrolyte. Based on this, the evaporation of liquid components during storage changes the composition, which reduces the conductivity. In addition, this method has a disadvantage of requiring a moisture-removing atmosphere, in which moisture is removed to a minimum, because the lithium salt contained in the liquid electrolyte reacts with moisture in the air to decompose.

US Patent Nos. 5,296,318 and 5,418,091 provide a mixed polymer electrolyte system to remedy the said deficiency. By adding a liquid electrolyte that is easily affected by moisture before wrapping the battery, the advantages of the gel-type polymer electrolyte are utilized (the gel-type polymer electrolyte contains a large amount of liquid electrolyte, and the conductivity of lithium ions is carried out through the liquid phase, so it has Conductivity similar to that of liquid electrolytes), the mixed polymer electrolyte can minimize the influence of moisture on the electrolyte preparation method. However, since the liquid electrolyte is added after the electrolyte membrane is prepared, there should be a position capable of absorbing the liquid component or a force capable of penetrating the liquid component inside the electrolyte membrane. Finally, dibutyl phthalate is added as a plasticizer in the step of preparing the electrolyte membrane, and after the assembly of the battery is completed, the plasticizer is separated using an organic solvent such as alcohol or ether into a position capable of adsorbing liquid components. However, in the process of separating dimethyl phthalate using a chemical reaction, the method has disadvantages of low reproducibility, decreased yield, and difficulty in automatic control during mass production.

Therefore, the present inventors made an effort to solve the above-mentioned deficiencies in the prior art in Korean Patent Application No. 98-57030, by adding an adsorbent capable of adsorbing liquid electrolyte to the polymer matrix body, after battery assembly, during the activation process of the battery Introduce liquid electrolyte.

The electrolyte membrane of the solid electrolyte is prepared under a dry condition from an adsorbent and a polymer binder. The density structure of the polymer binder can be large or small. In order to show better lithium ion conductivity by improving the adsorption capacity of liquid electrolytes, solid electrolytes in which the three-dimensional structure of the electrolyte membrane is changed are required.

Detailed description of the invention

Therefore, the present invention strives to solve the disadvantages of the above-mentioned method for preparing a solid electrolyte, including adding an adsorbent capable of adsorbing a liquid electrolyte to a polymer matrix after battery assembly to form an electrolyte membrane. That is to say, the present invention enables the polymer matrix to produce a microporous structure while maintaining the mechanical strength of the electrolyte membrane itself, which not only facilitates the adsorption of liquid electrolytes, but also improves the conductivity of lithium ions in the solid electrolyte.

The term "electrolyte membrane" used in the specification refers to an electrolyte membrane prepared under dry conditions without any liquid electrolyte. The term "solid electrolyte" in the specification refers to said electrolyte membrane having ion conductivity by combining a liquid electrolyte. Although the solid electrolyte is not completely in a solid state because it contains a liquid electrolyte, it is still called a "solid electrolyte" in order to distinguish it from a liquid electrolyte, because the basic skeleton of the solid electrolyte contained in the electrolyte membrane is in a solid state. In addition, the term "adsorbent" used in the specification refers to a material capable of adsorbing a liquid electrolyte or a material capable of increasing the ability of a solid electrolyte to adsorb a liquid electrolyte.

The method of a finished battery refers to a method of combining a cathode and an anode, which are prepared separately, and an electrolyte membrane formed by rolling or extrusion is interposed between the cathode and the anode. When the electrolyte membrane is prepared by one of the methods, a liquid electrolyte is added to the assembled battery, which can minimize the restriction on moisture-proof conditions in the method. In addition, according to the method of the present invention, the site capable of adsorbing the liquid electrolyte is formed during the preparation of the electrolyte membrane, so that the step of separating the plasticizer is no longer required. Thus, the method has the advantage of simplifying operations, which not only reduces manufacturing costs, but also facilitates automatic operations and increases yields. Furthermore, when the electrolyte membrane is prepared by one of the methods described therein, the polymer matrix begins to form a microporous structure, which facilitates the transport of liquid electrolytes, which in turn improves the Li-ion capacity of solid electrolytes with the same amount of adsorbents. conductivity.

The solid electrolyte of the present invention comprises an electrolyte membrane composed of a microporous structure and containing an inorganic adsorbent and a liquid electrolyte with ion conductivity.

Said electrolyte membrane is preferably prepared by a phase change method. Examples of such methods include wet and dry methods. The wet method refers to a method of preparing an electrolyte membrane, which includes the following steps:

dissolving the mixture of sorbent and polymeric binder in a solvent suitable for the polymeric binder,

The resulting solution is converted into a membrane form,

exchanging said solvent with a non-solvent suitable for polymeric binders, and

The resulting substance is dried to form an electrolyte membrane.

In contrast, the dry method refers to a method of preparing an electrolyte membrane, including the following steps:

mixing the mixture of adsorbent and polymeric binder with a solvent capable of dissolving the polymeric binder, a non-solvent not capable of dissolving the polymeric binder, a pore former and a wetting agent,

forming the resulting mixture into film form, and

The resulting film was sufficiently dried.

The subsequent activation process (introduction of an ionically conductive liquid electrolyte into the prepared porous electrolyte membrane) can produce a solid electrolyte for rechargeable batteries.

Therefore, the solid electrolyte of the present invention can be prepared by introducing an adsorbent capable of adsorbing liquid electrolyte or increasing adsorption capacity into the interior of the electrolyte membrane to form a porous electrolyte membrane matrix, and then embedding the liquid electrolyte in the pores. The lithium ion conductivity of the solid electrolyte prepared in this way is about 1-3×10 ^-3 S/cm at room temperature.

Examples of adsorbents capable of adsorbing liquid electrolytes or increasing adsorption capacity include organic materials such as porous polymers and inorganic materials such as mineral particles.

As for porous polymer adsorbents, polypropylene, polyethylene, polystyrene and polyurethane can be used, the pores are formed by macromolecular functional groups being introduced into branched network polymers or by adjusting the method according to the invention parameters. Natural polymers such as wood chips, pulp and cork can also be used.

As for the inorganic adsorbent, one kind or two or more kinds of particles selected from mineral particles, composite oxide particles and mesoporous molecular sieves can be used. Examples of said mineral particles include mineral particles having a phyllosilicate structure such as clay, sodium mica, montmorillonite and mica. Examples of the composite oxide particles include zeolite, porous silica and porous alumina. Examples of mesoporous structure molecular sieves include mesoporous molecular sieves made of oxides such as silicon/polymer materials with a pore size of 2-30 nm. The mineral particles, composite oxides and mesoporous molecular sieves can be mixed together, and two or more adsorbents selected from the above-mentioned adsorbents can be used in combination.

Said inorganic adsorbent has better mechanical strength stability, thermal stability and electrochemical stability with respect to organic adsorbent (such as porous polymer), thus the performance of the rechargeable battery using inorganic adsorbent is better than using organic Performance of Sorbent for Rechargeable Batteries.

That is, when the anode and cathode are assembled by extrusion or lamination to make a battery, the mechanical strength and thermal stability of the organic adsorbent are different from the electrolyte membrane or polymer binder of the composite electrode, so the use of the organic adsorbent Compared with rechargeable batteries using inorganic adsorbents, the discharge capacity of rechargeable batteries is significantly reduced during repeated charging and discharging. For example, adsorbents composed of organic materials such as polymers with low melting points or poor mechanical strength lose their adsorption capacity during extrusion or lamination. In other words, the use of organic adsorbents such as polymers may benefit the performance of electrolyte membranes or solid electrolytes themselves, but it is difficult to maintain their initial properties when batteries are fabricated by extrusion or lamination methods.

Furthermore, as explained above, since the transport of polymer chains directly affects the ionic conductivity of the polymer electrolyte, the effect of temperature on the ionic conductivity is important. Specifically, at low temperatures, the transport of the polymer chains is weakened, which greatly reduces the ionic conductivity, thereby deteriorating the performance of the resulting battery. However, the adsorbent used in the present invention increases the conductivity of ions. In addition, the influence of temperature can be reduced if inorganic adsorbents that are not affected by temperature are used in large quantities, which is different from the properties of general polymer electrolytes. Since the electrolyte contains a large amount of inorganic adsorbents, it has the advantage of improved resistance to combustion and detonation relative to electrolytes containing a large amount of organic materials such as polymers.

Therefore, it is preferable to use an inorganic adsorbent rather than an organic adsorbent in the composition of the electrolyte membrane of a rechargeable battery.

The added adsorbent is 30-95% by weight relative to the dry electrolyte membrane without liquid electrolyte, preferably 50-90%. If the added amount exceeds 95% by weight, the mechanical strength of the resulting electrolyte membrane decreases. If the added amount is not more than 30% by weight, the ability of the electrolyte membrane to absorb liquid electrolyte decreases.

The particle size of the adsorbent is preferably not more than 40 μm, more preferably not more than 20 μm, so as not to reduce the mechanical strength and uniformity of the electrolyte membrane.

As for the polymer binder, the most commonly used polymers can be used. Among them, preferably one or two or more selected from the following: polyvinylidene fluoride, copolymer of 1,1-ethylene fluoride and hexafluoropropylene, 1,1-bis Copolymers of vinyl fluoride and maleic anhydride, polyvinyl chloride, polymethyl methacrylate, polymethacrylate, cellulose triacetate, polyurethane, polysulfone, polyether, polyolefin (such as polyethylene or polypropylene), polyethylene oxide, polyisobutylene, polybutylene, polyvinyl alcohol, polyacrylonitrile, polyimide, polyvinyl formal, acrylonitrilebutyldiene rubber, ethylene- Propylene-diene-monomer, tetra(ethylene glycol) diacrylate, polydimethylsiloxane, polycarbonate and silicon polymer, or their copolymers.

The invention introduces the porous structure into the electrolyte membrane used as the matrix of the solid electrolyte, which is beneficial to the transfer of the liquid electrolyte, thus improving the lithium ion conductivity of the solid electrolyte by using the same amount of adsorbent. The method for preparing said porous electrolyte membrane as described above includes wet method and dry method. The wet process involves casting the electrolyte membrane components and then reacting the resulting membrane with a non-solvent to form a microporous structure on the polymer matrix. The dry process is to mold the electrolyte membrane components together with a non-solvent and a pore-forming agent for making pores to form a microporous electrolyte membrane.

For solvents for dissolving polymer binders, mixtures of one or two or more solvents selected from the following: N-methylpyrrolidinone, dimethylformamide, di Methylacetamide, tetrahydrofuran, acetonitrile, cyclohexanone, chloroform, methylene chloride, hexamethylphosphoramide, dimethylsulfoxide, acetone, and dioxane.

As non-solvents for polymer binders, one or a mixture of two or more selected from the group consisting of water, ethanol, ethylene glycol, glycerol, acetone, Dichloromethane, ethyl acetate, butanol, pentanol, hexanol and ether.

As for the pore former, it is preferred to use one or a mixture of two or more of the following substances selected from the group consisting of: 2-propanol, resorcinol, trifluoroethanol, cyclohexanol, hexafluoroiso Propanol, methanol, and hemiacetals produced by the reaction of maleic acid and hexafluoroacetone.

As the impregnating agent, it is preferable to use a nonionic surfactant, for example, Triton X-100 (manufactured by Aldrich Company), Igepal DM-710 (manufactured by GAF Company).

A liquid electrolyte containing an adsorbent, which can be prepared by dissolving a lithium salt in an organic solvent, will be dissolved in the electrolyte membrane. In the present invention, the liquid electrolyte is adsorbed in the electrolyte membrane is defined as "activation".

The organic solvent is preferably a solvent with strong polarity and no reactivity with lithium metal, so as to increase the degree of dissociation of ions by increasing the polarity of the electrolyte and facilitate the movement of ions by reducing the local viscosity around the ions. Examples of such organic solvents include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, dimethylsulfoxide, 1,3-diox Hexylcycline, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, N,N-dimethylformamide, diglyme, triglyme, and tetraglyme. Specifically, the organic solvent is preferably a mixture of two or more solvents consisting of a high-viscosity solvent and a low-viscosity solvent.

Said lithium salt is preferably a lithium salt with low lattice energy and high degree of dissociation. Examples of such lithium salts include LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiSCN, LICF ₃ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ and LiC(CF ₃ SO ₂ ) ₃ . Mixtures of them can be chosen. The concentration of the lithium salt is preferably 0.5M-2M.

The liquid electrolyte is added in an amount of 30-90% by weight, preferably 40-85% by weight, based on the total weight of the electrolyte including the liquid electrolyte.

The solid electrolyte according to the present invention is characterized in that it is easy to prepare compared to existing polymer electrolytes; because the conduction of lithium ions is carried out through the liquid phase, the solid electrolyte has a higher ion conductivity; and is not affected by moisture or temperature effect until the solid electrolyte absorbs the liquid electrolyte or is activated.

In the following, the preparation method of the solid electrolyte with porous structure will be described in more detail. wet method

The porous solid electrolyte according to the present invention can be prepared through five steps, namely, mixing the adsorbent and the polymer binder, dissolving the resulting mixture, shaping, making the polymer backbone and drying/activating.

First, the powdered sorbent (with a particle size not exceeding 40 microns) and the polymeric binder are dry mixed in a closed vessel.

The resulting mixture of sorbent and polymeric binder is dissolved in a solvent suitable for the polymeric binder. The solid content in the mixed solution is preferably 5-50% relative to the total weight of the solution. If the content is not more than 5% by weight, the mechanical strength of the electrolyte membrane is reduced, and if the content is more than 50%, the polymer binder cannot be sufficiently dissolved, or the viscosity of the mixed solution becomes large, which are is unfavorable.

In order to promote the dissolution of the polymer binder and avoid the agglomeration of the adsorbent, the mixed liquid is stirred with a magnetic stirrer, a mechanical stirrer, a planetary stirrer or a high-speed dispersing mixer. When stirring, an ultrasonic stirrer can be used to prevent the sorbent from clumping or foaming during mixing. In addition, if necessary, the mixture can be defoamed and filtered.

After the polymer binder is completely dissolved and uniformly mixed with the sorbent, the resulting mixture is formed into a film of uniform thickness. For example, the mixture can be poured onto flat glass or a Teflon pan and cast to obtain a product of uniform thickness. On the other hand, the mixture can also be separated from a regular-space mold and then coated on a substrate consisting of a polymer film. Different approaches disclosed in other patent applications can be chosen. The thickness of the film is preferably controlled between 10-200 μm. If the film thickness is not more than 10 m, the mechanical strength will be lowered, and if the film thickness is more than 200 μm, the ion conductivity will be lowered, both of which are disadvantageous.

After casting the mixture into a film, the film is contacted with a non-solvent suitable for the polymer binder to separate the solvent suitable for the polymer binder in order to create porosity in the polymer matrix. For example, the solvent can be separated by soaking the membrane in a non-solvent bath containing the non-solvent. Therefore, it is preferable to mix miscible solvents and non-solvents. The time for immersing the membrane in the non-solvent pool ranges from 1 minute to 1 hour, depending on the type of solvent and non-solvent. If the time is shorter than the specified time, it is difficult to obtain sufficient pores. Conversely, if the time exceeds the specified time, the output will decrease, which is disadvantageous. The temperature of the cell is preferably 10°C-90°C, more preferably 20°C-80°C. If the temperature is lower than that, it is difficult to obtain sufficient pores. If the temperature is too high, the mechanical strength of the electrolyte membrane decreases, which is not preferable. In general, it is preferable to determine the generated porosity according to the amount of solvent in the mixed solution consisting of adsorbent, polymer binder and solvent. It is preferable to control the composition, temperature and time of solution mixing so that the porosity is determined according to the amount of solvent in the mixed solution.

After separation of the solvent and complete drying of the resulting membrane, a liquid electrolyte is introduced into the membrane. dry method

According to the present invention, the porous structure solid electrolyte is prepared by a dry method consisting of 4 steps, that is, mixing the adsorbent and the polymer binder, adding additives (solvent, non-solvent, pore forming agent, impregnating agent), casting and drying/ activation.

Powdered sorbent (particle size not exceeding 40 microns) and polymeric binder are dry mixed in a closed container. The resulting mixture of sorbent and polymeric binder is dissolved in a solvent suitable for the polymeric binder.

In order to promote the dissolution of the polymer binder and avoid the agglomeration of the adsorbent, the mixed liquid is stirred with a magnetic stirrer, a mechanical stirrer, a planetary stirrer or a high-speed dispersing mixer. When stirring, an ultrasonic stirrer can be used to prevent the sorbent from clumping or foaming during mixing. In addition, if necessary, the mixture can be subjected to defoaming and filtration steps.

After the polymer binder is completely dissolved and uniformly mixed with the adsorbent, a solvent that cannot dissolve the polymer binder is added, that is, a certain amount of non-solvent that will not cause the polymer binder to precipitate is added. In order to facilitate the formation of a microporous structure, it is preferred to add a pore forming agent and an impregnating agent. After the additive-added mixture is completely dissolved, the resulting mixture is molded into a film of uniform thickness. For example, the mixture can be poured onto flat glass or a Teflon pan and cast to obtain a product of uniform thickness. The mixture can be separated from a regular-space mold and coated on a substrate consisting of a polymer film. In addition to this, different approaches disclosed in other patent applications can be chosen. The thickness of the film is preferably controlled between 10-200 μm. If the film thickness is not more than 10 µm, the mechanical strength will decrease, and if the film thickness exceeds 200 µm, the ion conductivity will decrease, neither of which is preferable.

After the forming of the membrane is completed, the obtained electrolyte membrane is completely dried at 20° C. to 200° C., and then a liquid electrolyte is added thereto.

A disadvantage of the dry process compared to the wet process is the difficulty in dispersing or mixing the sorbent, polymeric binder and additives. When complete dispersion or mixing cannot be performed, (1) it is difficult to complete the uniform dispersion of pores or adsorbents by dry method, (2) it is not easy to mold the electrolyte membrane and (3) the mechanical strength and reproducibility are reduced. That is, if the pores or adsorbents cannot be uniformly dispersed, it can be confirmed that (1) when the electrolyte membrane is used as the electrolyte of an electrochemical cell, the cell reaction appears in an inhomogeneous localized state; (2) the casting molding of the membrane is difficult; And (3) reduced mechanical strength, these unfavorable factors limit the use of dry method.

In addition, the dry method requires the addition of non-solvent additives to form pores, and according to the principle of the dry method, the solvent should be evaporated (dried) to form pores before the non-solvent is added. If the non-solvent is evaporated before the solvent evaporates, pores cannot be formed. In this regard, the non-solvent should be non-volatile or have a higher boiling point than the solvent. Based on this, one problem with the dry method is the residual non-solvent. In other words, a non-solvent that has a higher boiling point than the solvent or is less volatile is difficult to completely remove from the electrolyte membrane during the drying process. Thus a separation step is also required for complete removal of the non-solvent (for example, separation with alcohol or ether or increasing the drying temperature sufficiently high). In addition, since the non-solvent is chemically and electrochemically unstable, if the non-solvent remains in the electrolyte membrane, it may cause an oxidation reaction or a reduction reaction during repeated charge and discharge of the battery. As a result, the performance of the battery is reduced, such as a drop in battery capacity or gas evaporation. The same problem also occurs with other additives than solvents. Since the electrolyte membrane to be prepared consists only of an adsorbent and a polymer binder, it is necessary to completely remove additives or the like, which complicates the process, and the reproducibility of the process is poor.

Therefore, it is preferable to prepare an electrolyte membrane or a solid electrolyte by a wet method rather than by a dry method.

The present invention relates to rechargeable batteries, especially rechargeable lithium batteries, wherein the porous solid electrolyte is used as the electrolyte.

The process of a finished battery refers to the combination of a cathode and an anode, which are prepared separately, with an electrolyte membrane formed by lamination, extrusion or winding in between. When the electrolyte membrane is prepared by one of the methods described, the liquid electrolyte is added after battery assembly, which minimizes the limitations of the method on the moisture-removing atmosphere. In addition, according to the present invention, the site capable of adsorbing the liquid electrolyte is formed during the process of preparing the electrolyte membrane, so that the process of separating the plasticizer is no longer required. Thus, the method has the advantages of reduced operating costs, ease of automatic operation, and increased yield due to simplification of the operating process. In addition, when the electrolyte membrane is prepared by the method, a microporous structure is formed on the polymer matrix, which facilitates the transfer of liquid electrolyte and improves the lithium ion conductivity with the same amount of solid electrolyte.

In one embodiment of the method for preparing a rechargeable battery, by using the solid electrolyte according to the present invention, in combination with the cathode and anode, and inserting the porous electrolyte membrane prepared by the above method, such a battery can be fabricated. This porous electrolyte membrane contains adsorbent powder and has a porous structure to facilitate the adsorption of liquid electrolyte. The cathode is electrically connected to a cathode current collector and the anode is electrically connected to an anode current collector. The assembly is activated to absorb the liquid electrolyte, thus producing a functional electrochemical cell.

Figure 1 shows a cross-sectional view of a rechargeable battery in which a solid electrolyte according to the present invention is used. The solid electrolyte (1) contains adsorbent powder (11) and liquid electrolyte, which is adsorbed during the activation process. The cathode (2) is electrically connected to the cathode current collector (22), and the anode (3) is electrically connected to the anode current collector (33).

The method of preparing the cathode and anode is as follows. The cathode or anode consists of a current collector and an active material layer. The active material layer includes an active material, a conductive material, a binder, and the like. In addition, different additives can be added in order to improve the performance of the battery. The current collectors, conductive materials, binders, and additives contained in the cathode or anode can be the same or different, depending on the goals to be achieved.

The current collector provides a pathway for movement of electrons generated in oxidation/reduction reactions, which occur at the cathode or anode. As for the current collector, ordinary lead plates, foils, stamped foils and etched foils can be used, depending on the performance and manufacturing method of the battery. Using lead plates can increase the filling speed of the active material, but it also complicates the fabrication method. Using foil improves battery performance and simplifies fabrication, but it reduces the compactness of the active material. Copper, aluminum, nickel, titanium, stainless steel, carbon, etc. can be used as the current collector. Generally, aluminum is used as the cathode and copper as the anode.

Active materials are the most important components in an electrochemical cell, since they determine the performance of the cell, since the charge/discharge (or oxidation/reduction reactions) of the cell take place on these materials. Furthermore, the active material occupies the largest content on the active material layer. As for the cathode active material, oxides or sulfides of transition metals, organic compounds, polymer compounds, and the like can be used. Preference is given to using oxide or polymer materials such as lithium cobalt oxide (Li _x CoO ₂ ), lithium nickel oxide (Li _x NiO ₂ ), lithium nickel cobalt oxide (Li _x Ni _y Co _1-y O ₂ ), Spinel lithium manganese oxide (Li _x Mn ₂ O ₄ ) and manganese dioxide (MnO ₂ ), etc. As the anode active material, alkali metals, alkaline earth metals, carbon, filter metal oxides or sulfur compounds, organic compounds or polymers, preferably carbon or polymer materials, can be used. It is important to select the active material according to the target performance when the battery is used.

Conductive material refers to the material added to the cathode or anode to improve the conductivity of electrons, usually carbon. Among them, the conductive material is preferably graphite, coke, activated carbon and carbon black, more preferably graphite and carbon black. One or two or more materials may be selected from the above group, regardless of whether they are synthetic materials or natural materials. The conductive material is added in an amount of 3-15% by weight relative to the total weight of the electrolytic material. If the total weight of the added conductive material does not exceed 3% by weight, the conductivity is lowered to cause a problem of overvoltage. If the weight exceeds 15% by weight, the energy density per unit volume decreases and the side reaction of the conductive material increases.

Adhesive refers to the ingredients added to improve the binding performance of active materials, generally polymers. The polymers used in the preparation of solid polymer films can serve as binders. The binder is preferably the same polymer as the electrolyte membrane or a polymer with compatibility. The binder is added in an amount of 15% by weight or less relative to the total weight of the electrolytic material. If the amount of the binder used is less than necessary, the binding property of the electrode is lowered. If the content of the binder exceeds 15% by weight, the processability and porosity of the electrode decrease.

Additives refer to the materials added to improve the performance of batteries or electrodes, which can be selected in a wide range according to the target performance or use. The additives added can improve the binding performance of the inside of the synthesized electrode or the current collector, induce the porosity or non-crystallinity of the synthesized electrode, improve the dispersibility of the constituent materials of the synthesized electrode, and prevent the active material from overcharging/overdischarging, recombination or removal Said reaction product, or improve the adsorption properties of the liquid electrolyte. In general, salts, organic/inorganic compounds, minerals, and polymers can be used as additives and optionally as adsorbents for the electrolyte membrane.

Next, a rechargeable lithium battery will be described in more detail according to the present invention.

The porous electrolyte membrane prepared by the above method (without the step of introducing liquid electrolyte) under dry solid state and the respectively prepared cathode and anode are assembled to form a battery, and the liquid electrolyte is adsorbed by the electrolyte membrane to form a rechargeable lithium battery. In order for the used solid electrolyte to have sufficient ionic conductivity, the solid electrolyte should undergo an activation step to absorb the liquid electrolyte. Through an activation step, the solid electrolyte can be used as an electrochemical cell. If the solid electrolyte does not pass through the activation step, the ionic conductivity at room temperature will be significantly reduced, which is not conducive to the use of the solid electrolyte itself as an electrode.

The preparation method of the cathode and/or anode assembled with the electrolyte membrane is as follows. Each mixture of cathode material or anode material is kneaded into a paste. The obtained paste is formed into a film by casting, coating and screen printing, and the obtained film is combined with a current collector to form a cathode and/or an anode by extrusion or lamination. In addition, the paste can also be directly coated on the current collector to form the cathode and/or anode.

A solid electrolyte paste composed of an adsorbent, a polymer binder, and a solvent is directly used on the surface of the electrode produced by the above method to form a battery in which an electrolyte film is formed on the electrode. A battery can also be composed by laminating or extruding separately prepared electrodes and electrolyte membranes. When a battery is prepared by the above method, the adhesive force between the electrode and the electrolyte membrane increases. However, it is difficult to adopt the former method when the electrodes and the electrolyte membrane are not compatible with each other, or when the electrodes or the electrolyte membrane are easily contaminated or lose their performance during their preparation. Furthermore, if the electrolyte membrane is prepared by a dry process, the electrodes may be contaminated with non-solvent or pore-forming agent (used to induce pore structure), which is unfavorable, specifically, when water is used as the non-solvent or pore-forming agent, If the water is not completely removed through the drying step, the performance of the battery will degrade. In addition, there is a problem that it is difficult to achieve a complete dry condition. In the latter method, although the disadvantage is that the adhesion between the electrodes and the electrolyte membrane is weak, its advantages are more obvious, simplifying the quality control, process design and use of equipment. Thus, the latter method is superior to the former method.

The electrolyte membrane prepared by the method of the present invention contains adsorbent, which has the advantage of higher mechanical strength compared with pure electrolyte membranes or other electrolyte membranes containing gel-type polymer electrolytes or plasticizers. Therefore, since the electrolyte membrane of the present invention does not change much in form during extrusion or lamination, it has the advantage of being mass-producible and having a low rate of defective products. That is to say, the electrolyte membrane prepared by the method of the present invention has the advantage of being suitable for extrusion or lamination, which is more conducive to quality control, process design and equipment selection.

Brief description of the drawings

Fig. 1 is a sectional view of a battery in which the electrolyte of the present invention is used.

Fig. 2 is a graph of linear sweep voltammetry measurement results to detect the electrochemical stability of the solid electrolyte of the present invention.

Fig. 3 shows the change in discharge capacity of the battery during repeated charging and discharging, in which the battery containing the solid electrolyte of the inorganic adsorbent is compared with the battery using the polymer adsorbent. Explanation of the numbers in the drawings

1: Solid electrolyte 11: Adsorbent powder

2: Cathode 22: Cathode current collector

3: Anode 33: Anode current collector

Embodiment of the invention

In the present invention, the solid electrolyte according to the present invention and the method of preparing a battery using the solid electrolyte are described in detail as follows. First, the preparation and performance testing of solid electrolytes are carried out. In addition, the solid electrolyte is assembled with the anode and cathode to form a battery, and then the process of battery performance testing is described. However, the present invention is not limited to these embodiments, and different modifications also fall within the protection scope of the present invention. Embodiment 1 (wet method)

The adsorbent and PVdF powder were loaded into 20 ml small glass test tubes and mixed with a magnetic stirrer for 5 minutes in a dry state. To the resulting mixture was added 4 ml of N-methylpyrrolidone and stirring was continued until the binder was completely dissolved. To prevent agglomeration between the binder particles, the resulting solution was subjected to ultrasonic agitation for 30 minutes while stirring. The prepared mixed solution was coated on a glass plate to a thickness of 100 μm. The coating layer was soaked in a non-solvent bath for about 10 minutes, then separated from the non-solvent bath and dried at 40°C for 1 hour. The porous electrolyte membrane thus produced was soaked in the electrolytic solution for about 10 minutes. After the liquid electrolyte was completely absorbed, the weight change was measured. Ionic conductivity can be measured by using the alternate current impedance method.

Table 1 summarizes the types of adsorbents and binders, and the properties of the porous solid electrolyte: capacity and conductivity. In order to compare the ability of porous solid electrolytes to adsorb liquid electrolytes, the adsorption capacity (Δ _ab ) is defined as follows:

Δ _ab = [Amount of adsorbed liquid electrolyte (mg)]/[Weight of electrolyte membrane (mg)]

Table 1 Example Adsorbent PVdF non-solvent liquid electrolyte _Δab Ionic conductivity mS/cm Mechanical strength type gram gram a Sodium mica 0.13 0.28 H ₂ O EC/DMC 1M LiPF ₆ 7.0 2.1 excellent b Sodium mica 0.17 0.26 H ₂ O EC/DMC 1M LiPF ₆ 6.8 2.2 excellent c Sodium mica 0.72 0.24 H ₂ O EC/PC 1M LiPF ₆ 6.9 1.9 excellent d Sodium mica 1.06 0.26 H ₂ O EC/PC 1M LiPF ₆ 7.5 1.8 excellent e Sodium mica 1.51 0.26 H ₂ O EC/DMC 1M LiPF ₆ 8.0 2.4 excellent f Sodium mica 2.00 0.26 H ₂ O EC/DMC 1M LiPF ₆ 8.5 2.5 excellent g Sodium mica 1.98 0.25 ethanol EC/DMC 1M LiPF ₆ 5.1 1.0 excellent h Zeolite 1.37 0.60 H ₂ O EC/DMC 1M LiPF ₆ 7.2 1.9 excellent 1 Zeolite 1.50 0.38 H ₂ O EC/DMC 1M LiPF ₆ 8.2 2.0 excellent j Zeolite 1.65 0.29 H ₂ O EC/DMC 1M LiPF ₆ 8.0 2.4 excellent k Montmorillonite 1.34 0.58 H ₂ O EC/DMC 1M LiPF ₆ 8.0 2.8 excellent l Montmorillonite 1.50 0.38 H ₂ O EC/DMC 1M LiPF ₆ 8.2 2.9 excellent m porous silica 1.35 0.59 H ₂ O EC/DMC 1M LiPF ₆ 8.5 2.4 excellent no Polypropylene 1.35 0.60 H ₂ O EC/DMC 1M LiPF ₆ 7.0 1.9 excellent o sawdust 1.35 0.60 H ₂ O EC/DMC 1M LiPF ₆ 7.4 2.0 excellent Embodiment 2 (wet method)

Sodium mica powder and binder powder were filled into 20 ml small glass test tubes and mixed with a magnetic stirrer in a dry state for 5 minutes. To the resulting mixture was added 4 ml of N-methylpyrrolidone and stirring was continued until the binder was completely dissolved. To prevent agglomeration between the adsorbent particles, the resulting solution was subjected to ultrasonic agitation for 30 minutes while stirring. The prepared mixed solution was coated on a glass plate to a thickness of 100 μm. The coating layer was soaked in a water bath for about 10 minutes, then detached from the water bath and dried at 40°C for about 1 hour. The porous electrolyte membrane thus produced was soaked in the electrolytic solution for about 10 minutes. After the liquid electrolyte was completely absorbed, the weight change was measured. Ionic conductivity can be measured by using an AC impedance method. The results are shown in Table 2.

Table 2 Example Sodium mica Adhesive liquid electrolyte _Δab Ionic conductivity mS/cm Mechanical strength gram type gram a 1.98 PVdF 0.24 EC/DMC 1M LiPF ₆ 8.1 2.4 excellent b 2.00 P(VdF-HFP) 0.26 EC/DMC 1M LiPF ₆ 8.0 2.6 excellent c 1.95 PAN 0.25 EC/DMC 1M LiPF ₆ 7.8 2.2 excellent d 2.00 PU 0.26 EC/DMC 1M LiPF ₆ 8.9 2.9 excellent e 1.98 pvc 0.25 EC/DMC 1M LiPF ₆ 7.4 2.0 excellent f 2.00 P(VdF-HFP) 0.26 EC/DMC 1M LiPF ₆ 8.5 2.5 excellent Embodiment 3 (dry method)

1.17 g of sodium mica and 0.5 g of P(VdF-HFP) powder were put into a 20 ml small glass test tube and stirred and mixed with a magnetic stirrer for 5 minutes in a dry state. To the resulting mixture was added 8 grams of acetone and stirring was continued until the binder was completely dissolved. To prevent agglomeration between the binder particles, the resulting solution was subjected to ultrasonic agitation for 30 minutes while stirring. To the resulting mixture was added 0.9 g of ethylene glycol, 0.1 g of Triton X-100, and 1.8 g of isopropanol, and the resulting mixture was ultrasonically stirred for about 10 minutes until the added mixture was uniformly mixed. The prepared mixed solution was coated on a glass plate to a thickness of 100 μm. The coating layer was dried at 40°C for about 2 hours, and then dried in a vacuum dryer at 50°C for about 6 hours. The porous electrolyte membrane thus prepared was soaked in EC/DMC 1M LiPF ₆ solution for about 10 minutes. After the liquid electrolyte was completely absorbed, the weight change was measured. The Δ _ab value measured by the change in weight was 7.5. The ion conductivity can be measured to be 2.0×10 ⁻³ S/cm by using an AC impedance method.

Embodiment 4 (comparative embodiment)

2 g of sodium mica and 0.26 g of PVdF were charged into a 20 ml small glass test tube and stirred and mixed with a magnetic stirrer for 5 minutes in a dry state. To the resulting mixture was added 4 ml of N-methylpyrrolidone and stirring was continued until the binder was completely dissolved. To prevent agglomeration between the binder particles, the resulting solution was ultrasonically stirred for 30 minutes while stirring. The prepared mixed solution was coated on a glass plate to a thickness of 100 μm. The coating layer was dried at 40° C. for about 2 hours, and then dried in a vacuum drier for about 6 hours. The temperature of the vacuum drier was controlled at about 50° C. The difference between this embodiment and Embodiments 1-3 is that there is no pore structure forming step in this method. The electrolyte membrane thus prepared was soaked in the electrolytic solution for about 10 minutes. After the liquid electrolyte was completely absorbed, the weight change was measured. Conductivity can be measured by using the AC impedance method. The ion conductivity measured at room temperature was 7.0×10 ^-4 S/cm.

Example 5

To measure the electrochemical stability of the porous solid electrolyte, stainless steel (#304) was used as the working electrode, lithium metal was used as the counter electrode, and the standard electrode was used for linear sweep voltammetry measurements. The electrochemical potential used in linear sweep voltammetry was derived from an open circuit voltage of 5.5 volts. The scan rate of linear sweep voltammetry was 10 mV/sec. The linear sweep voltammetry measurement result of the porous solid electrolyte prepared by embodiment 1-(f), 1-(j), 1-(l) and 2-(s) is respectively shown as A, B, C and D.

Example 6

In order to measure the performance of a battery using a solid electrolyte, an oxide cathode, a carbon anode, and a solid electrolyte according to the present invention were assembled into a finished battery, and then charge and discharge tests were performed on the finished battery. The finished battery is in the form of a laminate, prepared by laminating the cathode, anode, and electrolyte membrane to which the liquid electrolyte is absorbed. Use DC at the rate of reversible capacitor charging (C/2 rate) within 2 hours until the battery voltage is 4.2V, then use 4.2V DC again until the current drops to C/10mA. Next, using a discharge current, the discharge rate is such that the discharge voltage drops to 2.5 V or 2.75 V (C/2 rate) within 2 hours. The charge and discharge tests were repeated, and the change in discharge capacity with charge and discharge was measured. The cell composition and test results are summarized in Table 3 and shown in FIG. 3 . In Table 3, the solid electrolyte refers to the case when the liquid electrolyte is adsorbed by the electrolyte membrane. In addition, the solid electrolyte in Example 4 was not subjected to battery testing.

table 3 Example cathode anode solid electrolyte picture active material conductive material Adhesive additive active material conductive material Adhesive additive v _LiCoO2 carbon black PVdF Sodium mica graphite carbon black PVdF Sodium mica Ex.1-(e) Figure 3-E w _LiCoO2 carbon black PVdF Zeolite graphite carbon black PVdF Zeolite Ex.1-(j) Figure 3-F x _LiCoO2 carbon black PVdF Zeolite graphite carbon black PVdF Zeolite Ex.1-(n) Figure 3-G the y _LiCoO2 carbon black P(VdF-HFP) Zeolite graphite carbon black P(VdF-HFP) Zeolite Ex.3 Figure 3-H z LiMn ₂ O ₄ carbon black P(VdF-HFP) Sodium mica graphite carbon black P(VdF-HFP) Sodium mica Ex.2-(q) Figure 3-I

FIG. 3 shows the change in the initial discharge capacity during repeated charging and discharging of the batteries prepared by the various examples. From the test results, it can be confirmed that the use of solid-state adsorbents containing inorganic adsorbents (Example 6-v, w, z) shows better battery performance. Furthermore, it can also be confirmed that the use of the solid adsorbent prepared by the wet method according to the invention shows better battery performance than the solid adsorbent prepared by the dry method (Example 6-y). That is to say, solid electrolytes containing inorganic adsorbents and prepared by wet methods generally have a better impact on battery performance (charging and discharging performance, etc.), although the properties of the electrolyte membrane or solid electrolyte itself (ionic conductivity, mechanical Intensity, etc.) There was no significant difference.

Industrial Applicability

The characteristics of the microporous solid electrolyte according to the present invention are as follows:

They have high mechanical strength, which makes them suitable for fabrication into thin films;

They have higher ionic conductivity relative to liquid electrolytes due to the fact that the adsorbent introduced into the polymer matrix is suitable for absorbing liquid electrolytes and does not limit the transfer of lithium ions;

Unlike ordinary gel-type polymer electrolytes, lithium salts will decompose when encountering traces of water. They are not introduced during the preparation of electrolyte membranes so they do not require any special dehydration atmosphere;

Due to the electrochemical stability of the adsorbents therein, they have a wide electrochemical potential window; and

Due to the simple preparation method of electrolytes, they are amenable to automated mass production.

In addition, the microporous solid electrolyte according to the present invention can reduce the surface resistance between the electrolyte and the electrode due to the excellent combination between the cathode and the anode and the small change in volume after the introduction of the liquid electrolyte. Thus, the microporous solid electrolyte according to the present invention is suitable for use as an electrolyte for a rechargeable lithium battery. Compared with solid electrolytes containing organic adsorbents, solid electrolytes containing inorganic adsorbents show excellent mechanical strength stability, thermal stability, and electrochemical stability, so the discharge capacity does not decrease much during repeated charging and discharging. The wet method is more efficient and stable than the dry method when introducing a porous structure into the electrolyte. When using microporous solid electrolytes to make electrochemical cells, the microporous solid electrolytes show excellent performance, such as the above-mentioned reduction in discharge capacity is not much.

Claims (7)

1. be used for the solid electrolyte of rechargeable battery, comprise:

Thickness is 10-200 μ m and the dielectric film with microcellular structure; And

Percentage by weight is the liquid electrolyte with ionic conductivity of 30-90%, and described weight is based on the electrolytical gross weight that comprises liquid electrolyte,

Wherein said dielectric film contains the adsorbent that particle size is no more than 40 μ m, and its content is 30-95% with respect to the gross weight of the dry state dielectric film that does not contain liquid electrolyte by weight.

2. solid electrolyte according to claim 1, wherein said dielectric film prepares by wet method, may further comprise the steps:

The mixture of dissolving adsorbent and polymer adhesive in a kind of solvent that is applicable to polymer adhesive,

Make resulting solution be transformed into form membrane,

Exchange described solvent with a kind of non-solvent of polymer adhesive that is applicable to, and dry then resulting material.

3. solid electrolyte according to claim 1, wherein said dielectric film may further comprise the steps by dry process:

The mixture of dissolving adsorbent and polymer adhesive in a kind of solvent that is applicable to polymer adhesive,

In resulting solution, add non-solvent, pore-forming agent and the impregnating agent that is applicable to polymer adhesive, and

Make resulting mixture form film, the resulting film of intensive drying then.

4. one kind according to claim 2 or the 3 described solid electrolytes that are applicable to rechargeable battery, wherein

Described solid electrolyte prepares by activation process, and described activation process is that the liquid electrolyte with ionic conductivity absorbs in the described dielectric film, and

The preparation of the liquid electrolyte of described ionic conductivity is by one or both or multiple lithium salts being dissolved in the mixture that one or both or multiple organic solvent form, and described lithium salts is selected from LiClO ₄, LiBF ₄, LiPF ₆, LiAsF ₆, LiSCN, LiCF ₃SO ₃, LiN (CF ₃SO ₂) ₂, LiC (CF ₃SO ₂) ₃Described lithium salt is 0.5M-2M, described organic solvent is selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, carbonic acid Methylethyl ester, gamma-butyrolacton, 1,3-dioxane, oxolane, 2-methyltetrahydrofuran, methyl-sulfoxide, sulfolane, N, dinethylformamide, diethylene glycol dimethyl ether, triglyme and tetraethylene glycol dimethyl ether.

5. one kind according to claim 2 or the 3 described solid electrolytes that are applicable to rechargeable battery, wherein

Described adsorbent is one or both or the multiple mixture of being made up of following substances, and described material is selected from porous polymer particles such as polyethylene, polypropylene, polystyrene and polyurethanes, paper pulp, cellulose, cork and wood chip; Mineral grain such as clay, paragonite, montmorillonite and mica; Composite oxide particle such as zeolite, porous silica and Woelm Alumina; The aperture of being made up of oxide or polymer is the mesoporous molecular sieve of 2-30nm; And other commercially available adsorbent;

Described polymer adhesive is one or both or the multiple mixture of being made up of following substances, the white poly-inclined to one side vinylidene fluoride of described material choosing, 1, the copolymer of 1-difluoroethylene and hexafluoropropylene, the copolymer of vinylidene fluoride and maleic anhydride, polyvinyl chloride, polymethyl methacrylate, polymethacrylates, cellulose triacetate, polyurethanes, polysulfones, polyethers, polyethylene, polypropylene, polyethylene oxide, polyisobutene, polybutylene, polyvinyl alcohol, polyacrylonitrile, polyimides, polyvinyl formal, acrylonitrile butylidene rubber, ethylene-propylene-diene-monomer, four (ethylene glycol) diacrylate, dimethyl silicone polymer, Merlon and silicon polymer, or their copolymer;

The solvent of described dissolve polymer adhesive is one or both or multiplely is selected from the mixture that following substances is formed that described material comprises N-methyl pyrrolidone, dimethyl formamide, dimethylacetylamide, oxolane, acetonitrile, cyclohexanone, chloroform, carrene, hexamethyl phosphoramide, methyl-sulfoxide, acetone and dioxane; And

The described non-solvent that is applicable to polymer adhesive is one or both or the multiple mixture of being made up of following substances, and described material is selected from: water, ethanol, ethylene glycol, glycerol, acetone, carrene, ethyl acetate, butanols, amylalcohol, hexanol and ether.

6. solid electrolyte that is used for rechargeable battery according to claim 5, wherein said adsorbent are one or both or the multiple mixture of being made up of following substances, and described material is selected from mineral grain, composite oxide particle and mesoporous molecular sieve.

7. chargeable lithium cell is made by following step:

The mixture of dissolving adsorbent and polymer adhesive in a kind of solvent that is applicable to polymer adhesive,

Make resulting solution change film forming,

Exchange described solvent with a kind of non-solvent of polymer adhesive that is applicable to, dry resulting material forms the many micropores dielectric film that contains adsorbent,

With negative electrode and anode the be assembled together formation battery of prepared dielectric film with preparation respectively, and then

The liquid electrolyte that makes resulting battery absorption have ionic conductivity.

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