KR20020078318A - Electrolyte Comprising a Polyurethane Binder for a Lithium Polymer Battery and Battery Containing the Same - Google Patents

Abstract

PURPOSE: A polyurethane matrix polymer electrolyte for a lithium polymer battery and a lithium polymer battery containing the electrolyte are provided, which has the low crystallinity, high tensile strength and elasticity and good ion conductivity. CONSTITUTION: The polyurethane matrix polymer electrolyte comprises a porous polyurethane binder; a plasticizer selected from the group consisting of ethylene carbonate, propylene carbonate, tetraethylene glycol dimethylether and their mixtures; and a lithium salt selected from the group consisting of LiCF3,SO3, LiBF4, LiPF6, LiClO4 and LiTFSI. Preferably the porous polyurethane binder is prepared by cutting the polyurethane for the bumper of waste cars to the thickness of 100-300 micrometers. Preferably the plasticizer is a mixture of tetraethylene glycol dimethylether and ethylene carbonate in the ratio of 1:1 by volume or a mixture of propylene carbonate and ethylene carbonate in the ratio of 1:1 by volume; and the lithium salt is LiCF3, SO3.

Description

Polyurethane Binder-containing Polyelectrolyte for Lithium Polymer Battery and Battery Comprising the Same

The present invention relates to a polyurethane binder-containing polymer electrolyte for a lithium polymer battery and a battery comprising the same. More specifically, the present invention is a polymer having low crystallinity, high tensile strength and elasticity, and is easy to manufacture, and the porous polyurethane which is an environmentally friendly material that can recycle the discarded polyurethane for automobile bumpers is used as an electrolyte binder. It relates to a polymer electrolyte for a lithium polymer battery produced using and a battery comprising the same.

With the recent development of advanced technology, portable telephone devices such as mobile phones, PCS and PHS, portable TVs, portable AV devices such as MDP (mini-discplayer), MP3 player, portable OA devices such as notebook PC and PDA (Personal Digital Assistants) In many fields, miniaturized devices are rapidly spreading. Therefore, many studies have been conducted on secondary batteries having the best discharge performance as an energy source of small devices and electrolytes constituting the same.

Currently, secondary batteries mainly used in information and communication equipment are lithium-ion batteries, nickel-hydrogen batteries, nickel-cadmium batteries, etc., but nickel cadmium batteries and nickel-metal hydride batteries are gradually decreasing in demand due to lithium ion batteries or lithium polymer batteries.

The electrolyte used in the battery may be divided into a liquid electrolyte and a solid electrolyte in the form of a film. Liquid electrolytes have the disadvantage that cell performance is reduced due to leakage from the cell, while gel solid polymer electrolytes generally have the following advantages: First, there is a risk of liquid leakage in case of cell breakage. Second, by adopting a light and thin exterior material, the thickness can be made 1mm thinner than a lithium ion battery. Third, as the ion conductor, the electron conductivity is very low and the self discharge rate is low. Fourth, the adhesion between the electrode and the electrolyte is excellent. In addition, it is possible to apply a thin film of a large area. Fifth, the flexibility is higher than the inorganic solid electrolyte, it is easy to apply the coating is easy to manufacture. In addition, due to the high energy density of the polymer electrolyte, a large area thin film battery can be made, and it is advantageous in that it is light, chemically stable, and the manufacturing process is simple.

Therefore, in consideration of the low weight and high energy density of lithium, the non-toxicity of sulfur, the abundance of resources, and the low price, the interest in lithium / polymer electrolyte / sulfur batteries is increasing. .

As a study on lithium / polymer electrolyte / sulfur batteries, U.S. Patent No. 5,523,179 (Chu et al.) Used a positive electrode containing 50% by weight of sulfur, and α-PEO (α-Polyethylene oxide) and PVDF polymer electrolyte. It is disclosed that a discharge capacity of 450 mAh / g. Cathode (900 mAh / g. Sulfur) and a-PEO (amorphous PEO) as an electrolyte can obtain a discharge capacity of 900 mAh / g or more at room temperature. Carins et al. Also obtained a discharge capacity of 450 mAh / g.sulfur at room temperature using PEGDME electrolytes [Journal of Power Source, 89 (2000), 219-226].

Solid polymer electrolytes can dissociate salts, which are charge carriers, have excellent molecular flexibility and should be used to facilitate salt transport.

However, the solid polymer electrolyte has a low ion conductivity, which is difficult to apply to a high performance battery system. The ion conductivity of the solid polymer electrolyte hardly exhibits the ion conductivity in the range of 10 ⁻⁴ to 10 ⁻³ S / cm, which is required as about 10 ⁻⁵ S / cm at room temperature. Recently, as a method for improving the ionic conductivity of a solid polymer electrolyte, a research has been conducted to add a plasticizer having high ion conductivity to the polymer electrolyte.

The ionic conductivity of plasticized polymer electrolytes reported so far is about 6.4 × 10 ^-3 S / cm for PVDF (polyvinylidenefluoride) at room temperature [Periasamy et al., Journal of Power Sources, 88 (2000), 269-273], Polyacrylonitrile (PAN) is about 1 × 10 ^-3 S / cm [Dias et al., Journal of Power Sources, 88 (2000), 169-191], and polyvinylchloride (PVC) is 2 × 10 ^-3 S / cm. Alamgir et al., Journal of Power Sources, 54 (1995), 40-45, polymethyl-methacylate (PMMA) is known to be 3 x 10 ^-3 S / cm [Agnihotry et al., Electrochimica Acta, 44 (1999), 3121-3126].

The present inventors recycled the discarded automobile bumper polyurethane instead of the existing electrolyte polymer materials such as PVDF, PAN, PVC, PMMA, and the like and have a high dielectric constant plasticizer such as EC, PC, TG, or mixtures thereof. Using an electrolyte prepared by dissolving a lithium salt in a low cost to develop an electrolyte with excellent discharge characteristics and ion conductivity.

An object of the present invention is to provide a porous polyurethane, which is an environmentally friendly material that is easy to manufacture and can recycle the discarded polyurethane for automobile bumpers, as a binder of an electrolyte suitable for a lithium polymer battery.

Another object of the present invention is to provide a binder for an electrolyte of a lithium polymer battery by only cutting a conventional commercialized polyurethane or a discarded automobile bumper polyurethane with a cutter without a cumbersome processing procedure.

Still another object of the present invention is a lithium polymer battery comprising a polyurethane binder, a plasticizer selected from ethylene carbonate (EC), propylene carbonate (PC), tetraethylene glycol dimethylether (TG), and a mixture thereof, and a lithium salt. It relates to a polymer electrolyte.

Still another object of the present invention is to provide a high capacity lithium polymer battery using a polymer electrolyte prepared by impregnating a porous polyurethane with a binder containing a lithium salt containing electrolyte.

Still another object of the present invention is to provide an electrolyte having excellent ion conductivity and discharge capacity by adjusting the constituents of the plasticizer and the impregnation time.

The above and other objects of the present invention can be achieved by the present invention described below.

1 is a front view of a cutter for producing a porous polyurethane according to the present invention by cutting a thin commercially available polyurethane.

2 is an electron micrograph of a porous polyurethane according to the present invention.

3 is a graph showing the resistance of an electrolyte prepared by impregnating a porous polyurethane binder according to the present invention in a 1 M concentration electrolyte of LiCF ₃ SO ₃ lithium salt in a plasticizer TG (tetraethylene glycol dimethylether) at room temperature.

4 is a measurement of the resistance of an electrolyte prepared by impregnating a porous polyurethane binder according to the present invention in a 1 M concentration electrolyte of LiCF ₃ SO ₃ lithium salt in a plasticizer mixed with TG and EC (ethylene carbonate) in a volume ratio of 1: 1 at room temperature. It is a graph shown.

5 is a resistance measurement of an electrolyte prepared by impregnating a porous polyurethane binder according to the present invention in a 1 M concentration electrolyte of LiCF ₃ SO ₃ lithium salt in a plasticizer mixed with PC (Propylene carbonate) and EC in a volume ratio of 1: 1 at room temperature. It is a graph shown.

Figure 6 is a graph showing the discharge capacity of the electrolyte prepared by impregnating the porous polyurethane binder according to the present invention in a 1M concentration electrolyte of LiCF ₃ SO ₃ lithium salt in the plasticizer TG at room temperature.

FIG. 7 shows measured discharge capacity of an electrolyte prepared by impregnating a porous polyurethane binder according to the present invention in a LiCF ₃ SO ₃ lithium salt 1M concentration electrolyte in a plasticizer mixed with TG and EC in a volume ratio of 1: 1 at room temperature. It is a graph.

8 is a discharge capacity of an electrolyte prepared by impregnating a porous polyurethane binder prepared according to the present invention in a LiCF ₃ SO ₃ lithium salt 1M concentration electrolyte in a plasticizer mixed PC and EC in a volume ratio of 1: 1 at room temperature It is a graph shown.

9 is a graph showing the weight change of the electrolyte according to the impregnation time for each plasticizer type in the porous polyurethane-containing electrolyte prepared according to the present invention.

The present invention relates to a polyurethane binder-containing polymer electrolyte for lithium polymer batteries and a battery including the same, wherein the electrolyte is a porous polyurethane binder, ethylene carbonate (EC), propylene carbonate (PC), tetraethylene glycol dimethylether (TG), and these It is characterized by consisting of a plasticizer, and a lithium salt selected from the mixture of. The polymer electrolyte according to the present invention is a porous polyurethane polymer impregnated in an electrolyte in which lithium salt is dissolved in a plasticizer such as EC, PC, and TG, and when applied to a room temperature type lithium sulfur battery, 1200-1700 mAh / g.sulfur It may have a discharge capacity.

Polyurethane according to the present invention can be used by thinly cutting a commercially available high-density polyurethane or discarded automobile bumper polyurethane to a thickness of 100㎛ to 300㎛ using the cutter of FIG. The cutter of Figure 1 is used to cut the polyurethane thinly using a micro blade (micro tomb) as a self-produced equipment for processing in the state that can be used as a binder for the electrolyte according to the present invention. In the present invention, by using a binder that can be used simply by cutting waste resources or conventional commercialized polyurethane instead of the conventional binder for the electrolyte can reduce the manufacturing cost of the electrolyte and simplify the manufacturing process.

The plasticizers according to the invention are EC, TG, PC, or mixtures thereof, with the TG: EC = 1: 1 (volume ratio) and PC: EC = 1: 1 (volume ratio) mixtures being preferred. The lithium salt is mixed with the plasticizer at a concentration of 0.5 to 1.5 M (mole) to prepare a lithium salt-containing electrolyte solution. The lithium salt is used to increase the ion conductivity of the solid polymer electrolyte, and includes LiCF ₃ SO ₃ , LiBF ₄ , LiPF ₆ , LiClO ₄ , or LiTFSI (lithium trifluoro methane sulfonate imide), wherein LiCF ₃ SO ₃ is Most preferred.

The lithium salt and the plasticizer may be mixed homogeneously by a stirrer, a mixer, a ball mill, an ultrasonic wave, an attritor, and the like. The polyurethane film is impregnated into a lithium salt-containing plasticizer to prepare an electrolyte. Preparation of the specific electrolyte is within the range that can be easily carried out by those of ordinary skill in the art. In a preferred embodiment of the present invention, the lithium salt and the plasticizer are stirred for 12 hours in an argon atmosphere by a stirrer, and then the polyurethane film is impregnated into the lithium salt-containing plasticizer to prepare an electrolyte.

In the present invention, by using a polyurethane binder and adjusting the blending ratio of the mixture of plasticizers, it is possible to exhibit excellent ion conductivity and high discharge capacity than the conventional room temperature solid polymer electrolyte.

The electrolyte may further include an inorganic filler as necessary. The type and content of the inorganic filler to be used can be easily determined by those skilled in the art.

A lithium polymer battery consists of a positive electrode, a negative electrode, and an electrolyte system according to the present invention. The positive electrode and the negative electrode can be easily manufactured by those skilled in the art. In a preferred embodiment of the present invention, a lithium metal is used as an anode, and a sulfur electrode is used as a cathode. The sulfur electrode is sulfur, carbon, lithium salt, etc. in a solvent, stirred and coated on a glass plate, and dried to produce a film shape.

The invention can be better understood by the following examples, which are intended to illustrate the invention and are not intended to limit the scope of protection defined by the appended claims.

Example

Example 1A-1C: Preparation of Electrolyte

Example 1A Preparation of Polyurethane Polymer Electrolyte Containing Plasticizer TG

Using the cutter of Figure 1 was cut while varying the thickness of the porous polyurethane to 100㎛ ~ 300㎛. Figure 2 is an observation of the porous polyurethane with an electron microscope.

The cut polyurethane was made into a binder in the form of a film and then left in a dryer at 50 ° C. for two days to remove moisture.

1 M LiCF ₃ SO ₃ lithium salt was mixed with the plasticizer TG, and stirred for 12 hours in an argon atmosphere.

The polyurethane film was impregnated in a lithium salt-containing plasticizer to prepare an electrolyte. After the plasticizer was completely impregnated, the electrolyte was laminated in the order of SS (Stainless Steel) / Polyurethane Electrolyte / Stainless Steel (SS) in an argon atmosphere. In order to measure the ion conductivity of the room temperature type porous polyurethane electrolyte, the resistance of the electrolyte was measured by using an impedance meter.

Figure 3 is a graph showing the measurement of the resistance of the electrolyte at room temperature, Figure 9 is a graph showing the weight change of the electrolyte with the impregnation time.

Example 1B Preparation of Polyurethane Polymer Electrolyte Containing TG and EC Mixtures as Plasticizers

An electrolyte was prepared in the same manner as in Example 1A, except that a TG: EC = 1: 1 mixture (volume ratio) was used as a plasticizer, and discharge characteristics and ionic conductivity were measured.

Figure 4 is a graph showing the measurement of the resistance of the electrolyte prepared according to Example 1B at room temperature, Figure 9 is a graph showing the weight change of the electrolyte with the impregnation time.

Example 1C Preparation of Polyurethane Polymer Electrolyte Containing PC and EC Mixtures as Plasticizers

An electrolyte was prepared in the same manner as in Example 1A, except that a PC: EC = 1: 1 mixture (volume ratio) was used as a plasticizer, and discharge characteristics and ionic conductivity were measured.

Figure 5 is a graph showing the measurement of the resistance of the electrolyte prepared according to Example 1C at room temperature, Figure 9 is a graph showing the weight change of the electrolyte with the impregnation time.

Example 2A-2C: Preparation of Battery

Example 2A: Preparation of Battery Using TG Plasticizer-Containing Electrolyte

The electrolyte prepared in Example 1A was laminated in the order of an anode, an electrolyte, and an anode in an argon atmosphere to prepare a lithium / polyurethane electrolyte / sulfur battery.

Fabrication of Lithium / Sulfur Electrode

Lithium metal was used as an anode, and 20% sulfur electrode was used as a cathode. The 20% sulfur electrode was prepared as follows: Sulfur powder 0.175 g, carbon powder 0.16 g, PEO 0.3001 g, LiCF ₃ SO ₃ 0.0399 g was put in 44 ml of ACN (acetonitrile) and stirred for 24 hours on a glass plate. After the coating, the dried sulfur electrode was placed in a desiccator to dry at room temperature for 24 hours and completely dried in the polymer electrolyte.

In order to investigate the discharge capacity of the room temperature type lithium / polyurethane electrolyte / sulfur battery, the discharge capacity was measured using a discharge tester.

In the electrode test conditions, the break time was maintained for 30 minutes at room temperature, the discharge current density was 20 mA / cell, and the cutoff voltage was 1.5V. 6 is a graph measuring the discharge capacity of the battery, Table 1 shows the discharge capacity value.

Example 2B Preparation of Battery Using Plasticizer-Containing Electrolyte Consisting of TG and EC Mixtures

A battery was prepared as in Example 2A except that the electrolyte prepared in Example 1B was used, and the discharge capacity was measured. 7 is a graph measuring the discharge capacity of the battery, Table 1 shows the discharge capacity value.

Example 2C

A battery was prepared as in Example 2A except that the electrolyte prepared in Example 1C was used, and the discharge capacity was measured. 8 is a graph measuring the discharge capacity of the battery, Table 1 shows the discharge capacity value.

Example 2A Example 2B Example 2C Discharge Capacity (mAh / g.sulfur) 1650 1200 1210

3 to 8, the electrolyte resistance (190 kPa) of Example 1A is higher than that of the other plasticizer of Example 1B-1C, and thus the ion conductivity is lower. However, as shown in FIG. The discharge capacity was excellent at 1650 mAh / g.sulfur. The electrolytes of Examples 1B to 1C including EC had excellent ion conductivity compared to discharge characteristics with electrolyte resistances of 11 kPa and 8 kPa, respectively.

As shown in FIG. 9, the electrolyte of Example 1A and the electrolyte of Example 1B were almost constant in the amount of plasticizer impregnated after 0.5 hours, and in the case of the electrolyte of Example 1C, the amount of plasticizer impregnation was almost 6 hours later. It was constant.

The present invention is simple to manufacture using a porous polyurethane electrolyte, it is easy to purchase a binder polyurethane, in particular, there is an advantage that the price can be lowered by recycling the discarded polyurethane for automobile bumpers, and the conventional solid polymer electrolyte and The present invention has an effect of providing a porous polyurethane binder for a lithium polymer battery and an electrolyte including the same, capable of simultaneously satisfying similar ion conductivity and high discharge capacity.

Simple modifications and variations of the present invention can be readily understood by those skilled in the art, and all such variations or modifications can be considered to be included within the scope of the present invention.

Claims (5)

Porous polyurethane binders; Plasticizers selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), tetraethylene glycol dimethyl ether (TG), and mixtures thereof; And Lithium salts selected from the group consisting of LiCF ₃ SO ₃ , LiBF ₄ , LiPF ₆ , LiClO ₄ , and LiTFSI; Polyurethane polymer electrolyte for lithium polymer batteries. The polyurethane polymer electrolyte of claim 1, wherein the porous polyurethane binder is prepared by cutting a bumper polyurethane of a waste vehicle to a thickness of 100 to 300 μm. The polyurethane polymer electrolyte of claim 1, wherein the mixture of plasticizers is a mixture of TG: EC = 1: 1 (volume ratio) or PC: EC = 1: 1 (volume ratio). The porous polyurethane polymer electrolyte of claim 1, wherein the lithium salt is LiCF ₃ SO ₃ . The lithium polymer battery according to any one of claims 1 to 4, comprising a porous polyurethane polymer electrolyte, a negative electrode made of lithium metal, and a sulfur-containing positive electrode.