KR101723994B1 - Separator, method of manufacturing the same, lithium polymer secondary battery including the same, and method of manufacturing lithium polymer secondary battery using the same - Google Patents

Abstract

A separator, a separator, a lithium polymer secondary battery comprising the same, and a method of manufacturing a lithium polymer secondary battery using the same, wherein the inorganic particle having a reactive functional group on the surface thereof; And a substrate on which a coating layer containing the inorganic particles is placed.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a separator, a separator, a method of manufacturing the separator, a lithium polymer secondary battery including the same, and a method of manufacturing a lithium polymer secondary battery using the separator, USING THE SAME}

A separator, a separator, a lithium polymer secondary battery comprising the same, and a method of manufacturing a lithium polymer secondary battery using the same.

The lithium ion battery has many advantages such as a high energy density and a long lifetime characteristic than a nickel cadmium battery or a nickel metal hydride battery, and is attracting attention as an electronic device such as a smart phone and a tablet computer as well as a medium and large battery such as an electric automobile.

Accordingly, the safety of the battery has recently emerged as an important issue.

The separator is one of the core materials of the lithium secondary battery which prevents the internal short circuit by preventing the contact between the positive electrode and the negative electrode and provides the passage of lithium ion in the charging and discharging process, which greatly affects the safety of the battery. Polyolefin separators such as polyethylene and polypropylene are most widely used because of their excellent mechanical strength, chemical stability and low cost.

At the time when high energy density and long life of the secondary battery are required, the separator should satisfy not only high safety but also excellent performance. However, the general polyolefin-based separator has a disadvantage in that its performance is lowered due to low wettability of the organic electrolyte because it exhibits hydrophobicity, and a drawback is that heat shrinkage occurs when the separator is exposed to high temperature through a stretching process.

In order to overcome such a problem, research is being conducted to coat thermally stable ceramic materials such as silica and alumina on the separation membrane or to mix the same with the separation membrane itself.

In order to successfully develop a lithium secondary battery having improved safety, a polymer electrolyte having high ionic conductivity and excellent mechanical properties must be developed. Current liquid electrolytes used in lithium secondary batteries are liable to leak and lead to fire or explosion when they are heated at high temperatures, and thus they are very vulnerable to safety. On the other hand, when the gel polymer electrolyte is used, there is no fear of leaking, the safety of the secondary battery can be greatly improved, and the secondary battery can be manufactured in various forms.

A separator, a method of manufacturing a separator, a lithium polymer secondary battery including the same, and a method of manufacturing a lithium polymer secondary battery using the same.

In one embodiment of the present invention, inorganic particles in which reactive functional groups are located on the surface; And a substrate on which a coating layer containing the inorganic particles is placed.

The reactive functional group may be a reactive functional group capable of polymerization.

The reactive functional group may be a vinyl group.

The particle size of the inorganic particles may be 10 to 2,000 nm. More specifically, it may range from 200 to 1,000 nm. When the thickness is less than 200 nm, the dispersibility is low and it is difficult to coat uniformly on the substrate. When the thickness is more than 1,000 nm, the pore size of the coating layer is too large and the thickness of the coating layer can not be appropriately controlled.

The inorganic particles include fluorides of Si, Sn, Ge, Cr, Al, Mn, Ni, Zn, Ti, Co, In, Cd, Bi, Pb and V; Oxides thereof; Or a combination thereof. However, the present invention is not limited thereto.

The substrate may be a polyolefin resin, a fluorine resin, a polyester resin, a polyacrylonitrile resin, a cellulose resin, a nonwoven fabric, or a combination thereof. More specifically, the substrate may be formed of a polyolefin-based resin such as polyethylene and polypropylene, a fluororesin such as polyvinylidene fluoride and polytetrafluoroethylene, a polyester-based resin such as polyethylene terephthalate and polybutylene terephthalate, Polyacrylonitrile resin and cellulose-based microporous membrane or non-woven fabric. The substrate is not limited as long as it can be generally used for a separator of a battery.

The porosity of the separation membrane may be 30% or more. More specifically, it may range from 30 to 80%. When the porosity is less than 30%, the electrolyte impregnation amount is low and the ion conduction characteristics are deteriorated. When the porosity is too high, the mechanical properties of the membrane are deteriorated and the membrane is vulnerable to electrical short circuit.

The total thickness of the separation membrane may be 5 to 200 탆. More specifically, it may be 5 to 100 mu m. However, the present invention is not limited thereto.

The thickness of the coating layer in the separation membrane may be 0.1 to 20 탆. More specifically, it may be 1 to 10 mu m. When the above range is not satisfied, it is difficult to expect improvement in heat resistance and mechanical properties by the coating layer. Further, not only the ion migration resistance is increased but also the energy density of the secondary battery can be lowered.

The coating layer may further include a binder.

The binder may be selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride and hexafluoropropylene copolymer, polyvinyl acetate, polyethylene oxide, polymethyl methacrylate, polyvinyl chloride, polyurethane, polyacrylonitrile, ethylene vinyl acetate Co-polymers, carboxymethylcellulose, polyimides, or mixtures thereof. However, the present invention is not limited thereto.

The weight ratio of the binder to the inorganic substance in the coating layer may be from 1/99 to 99/1. More specifically, it may be 10/90 to 90/10. When the content of the binder in the coating layer is less than 10% by weight, the adhesion between the inorganic material and the separator substrate becomes weak. When the content of the binder exceeds 90% by weight, the porosity of the coating layer decreases and the effect of heat resistance and mechanical properties I can not.

In another embodiment of the present invention, there is provided a method of preparing a porous particle, comprising: preparing an inorganic particle raw material having a reactive functional group; Obtaining an inorganic particle having a reactive functional group on its surface through a chemical reaction of the inorganic particle raw material; The obtained inorganic particles; bookbinder; And a solvent to prepare a coating solution; And coating the coating solution on the substrate surface to form a coating layer.

The inorganic particle raw material having a reactive functional group may be vinyltrimethoxysilane (VTMS), vinytriethoxysilane (VTES), or a combination thereof.

In the step of obtaining the inorganic particles in which the reactive functional group is located on the surface through the chemical reaction of the inorganic particle raw material, the chemical reaction may be condensation and / or hydrolysis reaction. Any general chemical reaction can be used if the desired inorganic particles can be obtained.

The obtained inorganic particles; bookbinder; And a solvent to prepare a coating solution, the total content of the inorganic particles and the binder in the solution may be 1 to 30% by weight. In the case of this range, the effect of the desired coating layer can be achieved.

In another embodiment of the present invention, cathode; A separator according to an embodiment of the present invention; And a gel polymer electrolyte can be provided. The structure of the specific separation membrane is as described above, and a description thereof will be omitted. A more detailed description will be given in the following examples.

The negative electrode includes a current collector and a negative active material layer formed on the current collector, and the negative active material layer includes a negative active material.

The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

As a material capable of reversibly intercalating / deintercalating lithium ions, any carbonaceous anode active material commonly used in lithium ion secondary batteries can be used as the carbonaceous material. Typical examples thereof include crystalline carbon , Amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in the form of amorphous, plate-like, flake, spherical or fibrous type. Examples of the amorphous carbon include soft carbon (soft carbon) Or hard carbon, mesophase pitch carbide, fired coke, and the like.

Examples of the lithium metal alloy include lithium and a metal such as Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Alloys may be used.

As the material capable of doping and dedoping lithium, Si, SiO _x (0 <x <2), Si-C composite, Si-Q alloy (Q is an alkali metal, an alkaline earth metal, A transition metal, a rare earth element or a combination thereof and not Si), Sn, SnO ₂ , Sn-C composite, Sn-R (wherein R is an alkali metal, an alkaline earth metal, A rare earth element or a combination thereof, but not Sn). The specific elements of Q and R include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Sb, Bi, S, Se, Te, Po, or a combination thereof.

Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, and the like.

The negative electrode active material layer also includes a binder, and may optionally further include a conductive material.

The binder serves to adhere the anode active material particles to each other and to adhere the anode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, Such as polyvinyl chloride, polyvinyl fluoride, polymers comprising ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, Styrene-butadiene rubber, epoxy resin, nylon, and the like may be used, but the present invention is not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any material can be used as long as it does not cause any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, , Carbon-based materials such as carbon fibers; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; Conductive polymers such as polyphenylene derivatives; Or a mixture thereof may be used.

The current collector may be a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foil, a copper foil, a polymer substrate coated with a conductive metal, or a combination thereof.

The anode includes a current collector and a cathode active material layer formed on the current collector.

As the cathode active material, a compound capable of reversibly intercalating and deintercalating lithium (a lithiated intercalation compound) can be used. Concretely, it is possible to use at least one of complex oxides of cobalt, manganese, nickel or a combination of metals and lithium, and specific examples thereof include compounds represented by any one of the following formulas. Li _a A _{1 - b} R _b D ₂ wherein, in the formula, 0.90? A? 1.8 and 0? B? 0.5; Li _a E _{1 - b} R _b O _{2 - c} D _c , wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.05; LiE _{2 - b} R _b O _{4 - c} D _{c where} 0? B? 0.5, 0? C? 0.05; Li _a Ni _{1 -bc} Co _b R _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1 - b - c} Co _b R _c O _{2 - ?} Z _{? Wherein} 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1 -b- c} Co _b R _c O _{2 - ?} Z ₂ wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, and 0 <? Li _a Ni _{1 -b- c} Mn _b R _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, and 0 <? Li _a Ni _{1 -b- c} Mn _b R _c O _{2 - ?} Z _{? Where the} 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1 -b- c} Mn _b R _c O _{2 - ?} Z ₂ wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _b E _c G _d O ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, and 0.001 ≤ d ≤ 0.1; Li _a Ni _b Co _c Mn _d GeO ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, and 0.001 ≤ e ≤ 0.1; Li _a NiG _b O ₂ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a CoG _b O ₂ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a MnG _b O ₂ wherein, in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1; Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); QO _2; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiV ₃ O ₈ ; LiTO ₂ ; LiNiVO _4; Li _(3-f) J ₂ (PO ₄ ) ₃ (0? F? 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0? F? 2); And LiFePO _4.

In the above formula, A is Ni, Co, Mn or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof; D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; Z is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; T is Cr, V, Fe, Sc, Y or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

Of course, a compound having a coating layer on the surface of the compound may be used, or a compound having a coating layer may be mixed with the compound. The coating layer may comprise, as a coating element compound, an oxide, a hydroxide of a coating element, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, or a hydroxycarbonate of a coating element. The compound constituting these coating layers may be amorphous or crystalline. The coating layer may contain Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof. The coating layer forming step may be carried out by any of coating methods such as spray coating, dipping, and the like without adversely affecting the physical properties of the cathode active material by using these elements in the above compound. It is a content that can be well understood by people engaged in the field, so detailed explanation will be omitted.

The cathode active material layer also includes a binder and a conductive material.

The binder serves to adhere the positive electrode active material particles to each other and to adhere the positive electrode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl Polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-acrylonitrile, styrene-butadiene rubber, Butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like, but not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any conductive material can be used without causing any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, Metal powders such as black, carbon fiber, copper, nickel, aluminum, and silver, metal fibers, and the like, and conductive materials such as polyphenylene derivatives may be used alone or in combination.

As the current collector, Al may be used, but the present invention is not limited thereto.

The negative electrode and the positive electrode are prepared by mixing an active material, a conductive material and a binder in a solvent to prepare an active material composition, and applying the composition to a current collector. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein. As the solvent, N-methylpyrrolidone or the like can be used, but it is not limited thereto.

According to another embodiment of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: preparing a separator according to an embodiment of the present invention; Preparing an electrolyte precursor solution comprising a crosslinking agent, an initiator, and a liquid electrolyte; Injecting the electrolyte precursor solution into a secondary battery composed of the separator and the electrode; And crosslinking the injected electrolyte precursor solution to prepare a gel polymer electrolyte. The present invention also provides a method for producing a lithium polymer secondary battery.

1 is a schematic view illustrating a process of manufacturing a separation membrane of a lithium polymer secondary battery according to an embodiment of the present invention.

The crosslinking agent may include two or more functional groups. Examples of the specific crosslinking agent may include a vinyl group having a double bond, an acrylate group, a methacrylate group, or a combination thereof. However, the present invention is not limited thereto.

The initiator may be t-amyl peroxide, benzoyl peroxide, azobis compounds, or a combination thereof. However, the present invention is not limited thereto.

The content of the crosslinking agent in the electrolyte precursor solution may be 0.1 to 10 wt%. More specifically, it may be 0.1 to 5% by weight. This range covers a range in which the reactive functional groups of the present invention are less than the conventional crosslinker content due to the coated inorganic particles. This makes it possible to manufacture a lithium polymer secondary battery without deteriorating other battery characteristics.

The liquid electrolyte may be at least one selected from the group consisting of lithium perchlorate, lithium hexafluoroethane, lithium perchlorate, lithium hexafluorophosphate, lithium hexafluorophosphate, and lithium perchlorate in a mixed solvent such as ethylene carbonate, dimethyl carbonate, diethyl carbonate, propylenecarbonate, ethylmethyl carbonate, gamma butyrolactone, dimethoxyethane, Phosphate, lithium triflate, lithium bistrifluoromethylsulfonylimide, lithium tetrafluoroborate, salts thereof, or mixtures thereof. However, the present invention is not limited thereto.

A separator, a method of producing a separator, a lithium polymer secondary battery including the same, and a method of manufacturing a lithium polymer secondary battery using the same.

Such a separator not only exhibits excellent mechanical properties and thermal stability but also exhibits a solid electrode-separator-electrolyte interfacial property, thereby achieving excellent charge-discharge characteristics and cycle life.

1 is a schematic view illustrating a process of manufacturing a separation membrane of a lithium polymer secondary battery according to an embodiment of the present invention.
2 is an electron micrograph of reactive silica.
3 is an FT-IR spectrum of a reactive silica having a vinyl group.
4 is an electron micrograph of the separation membrane. More specifically, (a) is a polyethylene separator, and (b) is a separator coated with a reactive silica.
5 shows the wettability test results of the separator.
6 is a result of the heat shrinkage test of the separator.
7 shows the charge / discharge cycle results (25 ^° C, 0.2C rate) of a lithium metal polymer battery (Li powder / LiV ₃ O ₈ ).
8 is discharge capacity data according to the current density of a lithium metal polymer battery (Li powder / LiV ₃ O ₈ ).
9 is a charge-discharge cycle results in a lithium ion polymer battery _{(carbon / LiNi 1/3 Co} 1/3 Mn 1/3 O 2) (25 o C, 0.5C rate).
10 is a charge-discharge cycle results in a lithium ion polymer battery _{(carbon / LiNi 1/3 Co} 1/3 Mn 1/3 O 2) (55 o C, 0.5C rate).

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

As described above, in one embodiment of the present invention, the reactive inorganic particles having a reactive functional group (for example, a vinyl group) are coated on the separation membrane and the reactive functional groups participate in the crosslinking reaction, thereby reducing the crosslinking agent content, And the interface resistance between the electrode and the separator is reduced.

Research is actively underway to improve thermal stability by coating existing inorganic materials on the membrane.

For example, in Korean Patent Application No. 2002-0080797, linear polymer and inorganic material are coated on both sides of a microporous membrane, a crosslinked polymer is impregnated on both surfaces thereof, a cathode is stacked on one side of the separator, Thereby minimizing battery resistance and ensuring excellent charge / discharge characteristics. Korean Patent Application No. 10-2009-0069411 discloses a process for producing a crosslinked ceramic coating separator containing an ionic polymer by strengthening the binding force between the coating material and the porous film substrate through chemical crosslinking to thereby suppress the peeling phenomenon of the coating material, Thereby improving the cycle characteristics of the lithium secondary battery. Korean Patent Application No. 10-2013-0037386 provides a separation membrane coated with a water-dispersed ceramic slurry on one side or both sides of a porous substrate to reduce the decrease in air permeability due to the coating layer and contributes to high capacity and high output of the secondary battery by thin coating .

In Korean Patent Application No. 10-2013-0027210, by applying an inorganic oxide thin film to a porous substrate, it is possible to assemble a battery having high ion diffusivity and at the same time, improving thermal characteristics at a high temperature, thereby preventing internal short-circuiting.

The above-mentioned conventional inorganic material coating separator has the main objective of improving mechanical properties and thermal stability. These may cause a problem that the inorganic substances are desorbed during the winding process or the charging / discharging process, the adhesiveness between the separator and the electrode is poor, and the electrolyte may escape to the outside of the battery, thereby deteriorating the characteristics of the secondary battery. When a gel polymer electrolyte is synthesized by chemical crosslinking after an inorganic material is coated on a separator, the crosslinking agent content must be maintained at a high level for sufficient crosslinking, resulting in a disadvantage that high-rate discharge characteristics are poor.

In the case of using the separator which is one embodiment of the present invention, the mechanical strength of the separator can be improved due to the coating of the inorganic particles, and the heat shrinkage rate at high temperature can be greatly reduced. Also, the wettability with respect to the electrolytic solution can be improved, and the ion conduction characteristics can be improved. In addition, the reactive functional groups existing on the surface of the inorganic particles facilitate the crosslinking reaction, and the crosslinking reaction can be performed with a small amount of the crosslinking agent. Thus, the adhesion between the electrode and the separator can be improved and the lifetime characteristics of the battery can be improved.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

Vinyl  Synthesis of Reactive Silica

Vinyltrimethoxysilane (hereinafter referred to as VTMS) is quantitatively measured and slowly dropped into a reactor containing distilled water, followed by stirring. When VTMS is completely dispersed in distilled water and the solution becomes transparent, a certain amount of aqueous ammonia solution is added and stirred for 12 hours at room temperature to proceed the condensation and hydrolysis reaction.

After the reaction is completed, the obtained solution is centrifuged to obtain a precipitate. The precipitate is washed three times or more with methanol and filtered to obtain a product in which unreacted materials and impurities are removed. When they are dried in a vacuum oven at 70 DEG C for 1 hour, a reactive silica having a vinyl group is finally obtained. An electron micrograph of the reactive silica having various sizes (particle diameter: 300, 600, 900 nm) thus obtained is shown in FIG.

2 is an electron micrograph of reactive silica. Specifically, (a) diameter is 300 nm, (b) diameter is 600 nm, and (c) diameter is 900 nm.

FIG. 3 shows the FT-IR spectrum of the reactive silica having a particle diameter of 300 nm. It is confirmed that a vinyl group capable of polymerization is present in the silica particles through the infrared absorption region appearing at 1600 cm ^-1 and 1400 cm ^-1 have.

Preparation of separator coated with reactive silica

The coating separator is prepared by coating the surface of the separator with a reactive silica and a binder. First, reactive silica and a poly (vinylidene fluoride-hexafluoropropylene) copolymer were mixed in a weight ratio of 7: 3, and the resultant mixture was added to an acetone solvent at a concentration of 5% by weight. Butanol was added in an amount of 10% Prepare the coating solution.

The obtained coating solution is coated on one side of the polyethylene separator using a bar having a predetermined gap, and after drying at room temperature, it is coated on the opposite side not coated with the same method.

When they are dried in a vacuum oven at 70 캜 for 12 hours or more, a separation membrane coated with a reactive silica can be obtained.

The thickness of the coating separation membrane thus obtained is in the range of 2 to 4 占 퐉 as summarized in Table 1 below, and an electron micrograph of the separation membrane coated with the reactive silica is shown in FIG. More specifically, FIG. 4A is a polyethylene separator, and FIG. 4B is a separator coated with reactive silica (particle diameter: 300 nm).

system Thickness (㎛) Electrolyte impregnation rate (%) Ion conductivity (S / cm) Heat shrinkage (%) PE separator 9 160 1.5 X 10 ^-4 11.8 The coating separator (particle diameter: 300 nm) 11 214 4.7 X 10 ^-4 <2 The coating separator (particle diameter: 600 nm) 12 200 4.1 X 10 ^-4 <2 The coating separator (particle diameter: 900 nm) 13 197 3.5 X 10 ^-4 <2

* Thickness of membrane, electrolyte impregnation rate, ionic conductivity, heat shrinkage at 130 ℃

Physical Properties of Reactive Silica-Coated Membrane

Coated membranes were prepared by coating reactive silica having particle diameters of 300, 600, and 900 nm, respectively, on both sides of the separator, and physical properties were compared with the polyethylene separator used as a support.

The electrolyte impregnation rate test was performed by immersing the separator in a liquid electrolyte for a predetermined time and measuring the amount of the absorbed electrolyte. Ion conductivity was also measured after synthesis of the gel polymer electrolyte using each membrane. The liquid electrolyte was prepared by dissolving 1.15 M of LiPF ₆ in a mixed solvent of ethylene carbonate (EC) / ethylmethyl carbonate (EMC) / diethyl carbonate (DEC) (volume ratio = 30/50/20) Was used.

As a result, the results shown in Fig. 5 and Table 1 were obtained. 5 shows the wettability test results of the separator. More specifically, the present invention relates to a polyethylene separator (b) coating separator (particle diameter: 300 nm), (c) a coating separator (particle diameter: 600 nm), and (d) a coating separator (particle diameter: 900 nm).

From the above results, it can be seen that the coating of the reactive silica increases the space in which the electrolyte can be impregnated into the void space between the inorganic particles, and the electrolyte solution impregnation rate and the ionic conductivity are improved by increasing the moisture absorption rate of the electrolyte due to the introduction of the silica and the binder. Also, as the inorganic particle size used for coating the separator decreased, electrolyte impregnation rate and ion conductivity increased.

Next, the thermal shrinkage of the membrane after storage at high temperature was compared. The membrane was cut into 5 ㎝ X 5 ㎝ and allowed to stand at 130 캜 for 30 minutes. The heat shrinkage was calculated by measuring the size of the membrane. The results are shown in Fig. 6 and Table 1 above. 6 is a result of the heat shrinkage test of the separator. More specifically, the present invention relates to a polyethylene separator (b) coating separator (particle diameter: 300 nm), (c) a coating separator (particle diameter: 600 nm), and (d) a coating separator (particle diameter: 900 nm).

The polyethylene separator left at high temperature produced severe heat shrinkage, but the coating separator hardly showed any heat shrinkage regardless of the size of the inorganic material used. It can be seen that the thermal stability of the separator is greatly improved by coating the inorganic material.

Lithium metal Polymer  battery( Li / LiV ₃ O ₈ ) &Lt; / RTI &gt; &lt; RTI ID = 0.0 &

A lithium metal polymer battery composed of a Li-powder cathode and a LiV ₃ O ₈ anode was prepared using a separator coated with a reactive silica. The anode is composed of LiV ₃ O _{8 as an} active material, Ketjenblack as a conductive material, and SBR / CMC as a binder.

Active material: Conductive material: The binder was mixed with distilled water at a weight ratio of 80: 15: 5, cast on an aluminum current collector, and dried at 110 DEG C for 12 hours to prepare an electrode. The precursor solution for synthesizing the gel polymer electrolyte was prepared by dissolving tetraethylene glycol diacrylate (3.5% by weight), which is a crosslinking agent, in a liquid electrolyte in which 1.15 M LiTFSI was dissolved in a mixed solvent of EC / DEC (volume ratio = 30/70) t-amyl peroxypivalate (1% by weight).

The separation membrane was composed of a polyethylene separator and a separator coated with 300 nm reactive silica.

The electrolyte precursor solution was injected into a secondary battery and thermally crosslinked at 70 ° C. for 1 hour to prepare a lithium metal polymer battery in which a gel polymer electrolyte was crosslinked on the electrode and the separator. The results of charging / discharging experiments at a current density of 0.2 C at a voltage range of 1.5 to 4.0 V at 25 占 폚 are shown in Fig. 7 shows the charge / discharge cycle results (25 ^° C, 0.2C rate) of a lithium metal polymer battery (Li powder / LiV ₃ O ₈ ). As a result of the charge / discharge test up to 200 times, the separator coated with the reactive silica exhibited excellent charge / discharge life characteristics.

In order to compare discharge characteristics at a high rate, the discharge current density was changed to 0.1C, 0.2C, 0.5C, 1.0C, 2.0C, and 0.1C, and the high rate discharge characteristics of the lithium metal polymer battery were evaluated.

8 is discharge capacity data according to the current density of a lithium metal polymer battery (Li powder / LiV ₃ O ₈ ). It can be seen that the separator coated with the reactive silica shows excellent characteristics. The excellent charge-discharge characteristics and high-rate discharge characteristics of the separator coated with the reactive silica are attributed to the improved ionic conductivity and interfacial stability.

Lithium ion polymer  battery( carbon / LiNi _{One / 3} Co _{One / 3} Mn _{One / 3} O ₂ ) And evaluation of performance (2)

A lithium - ion polymer battery was fabricated using a separator coated with a reactive silica to evaluate its performance at room temperature and high temperature. Natural graphite was used for the cathode and LiNi _1/3 Co _1/3 Mn _1/3 O ₂ was used for the anode. The negative electrode was prepared by mixing natural graphite, a conductive material (super-P) and a binder (polyvinylidene fluoride) in an NMP solvent at a ratio of 85: 7.5: 7.5 and then casting on a copper collector. The anode _{LiNi 1/3 Co 1/3} Mn 1/3 O 2, the conductive material (super-P), a binder (polyvinylidene fluoride) 85: 7.5: was mixed in NMP solvent at a 7.5 ratio of aluminum collector on Cast and then dried at 110 ° C for 12 hours.

As the electrolyte, 1.15 M LiPF ₆ EC / EMC / DEC (volume ratio = 30/50/20) was used as the electrolyte and tetraethyleneglycol diacrylate (3.5 wt%) as a crosslinking agent and t-amyl peroxypivalate %) Was added to prepare a precursor electrolyte solution. The charge and discharge lifetime characteristics of lithium polymer batteries were compared at 25 ℃ and 55 ℃.

As a result of the charge and discharge tests at a current density of 0.5 C in the voltage range of 3.0 to 4.5 V, the separator coated with the reactive inorganic material at room temperature and high temperature was better and the capacity and the life characteristic were higher when the reactive silica size was small.

9 is a charge-discharge cycle results in a lithium ion polymer battery _{(carbon / LiNi 1/3 Co} 1/3 Mn 1/3 O 2) (25 o C, 0.5C rate). 10 is a charge / discharge cycle result (55 ^° C, 0.5C rate) of a lithium ion polymer battery (carbon / LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ).

As can be seen from Figs. 9 and 10, the reactive silica suppresses the formation of HF produced by pyrolysis of LiPF ₆ , thereby improving lifetime characteristics at high temperature.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (22)

Inorganic particles in which the reactive functional groups are located on the surface; And
And a substrate on which a coating layer containing the inorganic particles is disposed,
The reactive functional group is a vinyl group capable of free radical polymerization,
Wherein the total thickness of the separation membrane is 11 to 13 占 퐉, the thickness of the coating layer in the separation membrane is 2 to 4 占 퐉, and the particle size of the inorganic particles is 300 to 900 nm.
Membrane.
delete delete delete delete The method according to claim 1,
Wherein the substrate is a polyolefin resin, a fluorine resin, a polyester resin, a polyacrylonitrile resin, a cellulose resin, a nonwoven fabric, or a combination thereof.
The method according to claim 1,
Wherein the separation membrane has a porosity of 30% or more.
delete delete The method according to claim 1,
Wherein the coating layer further comprises a binder.
11. The method of claim 10,
The binder may be selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride and hexafluoropropylene copolymer, polyvinyl acetate, polyethylene oxide, polymethyl methacrylate, polyvinyl chloride, polyurethane, polyacrylonitrile, ethylene vinyl acetate Cellulose methyl cellulose, polyimide, or a mixture thereof.
11. The method of claim 10,
Wherein the weight ratio of the binder to the inorganic substance in the coating layer is 1/99 to 99/1.
Preparing an inorganic particle raw material having a reactive functional group;
Obtaining inorganic particles through chemical reaction of the inorganic particle raw material;
The obtained inorganic particles; bookbinder; And a solvent to prepare a coating solution; And
And coating the coating solution on the substrate surface to form a coating layer,
The inorganic particle raw material having a reactive functional group is preferably selected from the group consisting of vinyltrimethoxysilane (VTMS), vinytriethoxysilane (VTES)
The reactive functional group is a vinyl group capable of free radical polymerization,
Wherein the chemical reaction is a condensation and hydrolysis reaction, silica in which a reactive functional group is located on the surface is obtained as the inorganic particles, and the inorganic particles are obtained by reacting the inorganic particles The particle diameter is 300 to 900 nm,
Applying the coating solution to a substrate surface to form a coating layer; And a substrate on which a coating layer containing the inorganic particles is placed,
Wherein the total thickness of the separation membrane is 11 to 13 mu m and the thickness of the coating layer in the separation membrane is 2 to 4 mu m.
(2).
delete delete 14. The method of claim 13,
The obtained inorganic particles; bookbinder; And a solvent to prepare a coating solution,
Wherein the total content of the inorganic particles and the binder in the solution is 1 to 30% by weight.
anode;
cathode;
12. A separation membrane according to any one of claims 1, 6, 7, and 10 to 12; And
Gel polymer electrolyte. &Lt; IMAGE &gt;
16. A method for manufacturing a semiconductor device, comprising: preparing a separation membrane according to claim 13 or 16;
Preparing an electrolyte precursor solution comprising a crosslinking agent, an initiator, and a liquid electrolyte;
Injecting the electrolyte precursor solution into a secondary battery composed of the separator and the electrode; And
Crosslinking the injected electrolyte precursor solution to prepare a gel polymer electrolyte;
Wherein the lithium polymer secondary battery is a lithium polymer secondary battery.
19. The method of claim 18,
Wherein the crosslinking agent comprises two or more functional groups.
19. The method of claim 18,
Wherein the content of the crosslinking agent in the electrolyte precursor solution is 0.1 to 10 wt%.
19. The method of claim 18,
Wherein the initiator is t-amyl peroxide, benzoyl peroxide, an azobis compound, or a combination thereof.
19. The method of claim 18,
The liquid electrolyte may be at least one selected from the group consisting of lithium perchlorate, lithium hexafluoroethane, lithium perchlorate, lithium hexafluorophosphate, lithium hexafluorophosphate, and lithium perchlorate in a mixed solvent such as ethylene carbonate, dimethyl carbonate, diethyl carbonate, propylenecarbonate, ethylmethyl carbonate, gamma butyrolactone, dimethoxyethane, Phosphate, lithium triflate, lithium bistrifluoromethylsulfonylimide, lithium tetrafluoroborate, a salt thereof, or a mixture thereof.

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