KR100513185B1 - Solid electrolyte for lithium secondary battery - Google Patents

Abstract

The present invention relates to a solid electrolyte for a lithium secondary battery, wherein the solid electrolyte for a lithium secondary battery of the present invention is Li, P, X, O and N (wherein the molar ratio of X to P (X / P) is 1 or less and X is A solid electrolyte for a five-membered thin film battery containing five atoms of B), Si, Al, Ge, and As). Where P and X are substances forming the skeleton of the network, and N is a substance forming the network structure by modifying the skeleton of the network.

Description

Solid electrolyte for lithium secondary battery {SOLID ELECTROLYTE FOR LITHIUM SECONDARY BATTERY}

[Industrial use]

The present invention relates to a solid electrolyte for lithium secondary batteries of the present invention, and more particularly, to a solid thin film electrolyte for lithium secondary batteries having two or more network formers.

[Prior art]

Batteries that convert chemical energy into electrical energy have been widely used due to their high energy conversion efficiency and simple structure. Among them, lithium batteries have high potential and high energy density, which is one of the most active researches in the field of batteries today.

These lithium batteries are basically composed of a negative electrode (e.g., lithium metal, a lithium alloy and graphite capable of removing and inserting lithium), a positive electrode (e.g. LiCoO ₂ , Li ₂ MnO ₄ and V ₂ O ₅ ), and an electrolyte. . One of the most closely related to the performance of the battery today is the electrolyte that provides the passage of lithium ions.

Examples of electrolytes for lithium batteries include liquid electrolytes and solid electrolytes. The liquid electrolyte is an electrolyte widely used in a conventional lithium battery and has an advantage of exhibiting high ionic conductivity. However, this is basically an acid solution, which is environmentally undesirable and poses a problem of leakage. In order to solve this problem, a solid electrolyte is proposed, which can be roughly classified into a solid polymer electrolyte and a solid thin film electrolyte.

Solid polymer electrolytes are based on the discovery that a polymer matrix composed of polyethylene oxide (PEO) has conductivity to lithium ions. It is under development.

 However, such a solid polymer electrolyte is basically assumed to be used in a bulk battery, and its use is limited to an electrolyte for a thin film battery having a total size of only a few μm.

Solid oxide electrolytes are emerging as electrolytes for thin-film batteries, and basically include network modifiers that form the backbone of the network and network modifiers that modify the backbone of the network, and further add lithium ion to the network. May include a network dopant to enhance. Representative examples of such solid thin film electrolytes include U.S. Patent No. 5,338,625, which includes Li-P-O-N as a component, and U.S. Patent No. 5,455,126, which is a divided application thereof.

The solid thin film electrolyte of the US patent has a network forming agent for forming a network skeleton, and has a Li-PO, and a network modifier for forming a net structure by modifying the network skeleton by cutting, condensation polymerization, and branching the network skeleton. has N as its (network modifier).

However, despite the above-mentioned US patent, the development of a solid thin film electrolyte is still in its infancy, and there is a demand for the development of various types of polymer oxide electrolytes that can provide better battery performance.

In order to solve the above problems, an object of the present invention is to provide a new solid thin film electrolyte.

Another object of the present invention is to provide a five-membered solid electrolyte having two or more network formers.

Still another object of the present invention is to provide a method for preparing the solid electrolyte.

The above object and other objects of the present invention control the physical properties between the electrolyte constituent elements to change the bonding force and bonding structure between the constituents, thereby forming a high lithium ion conductivity, low electron conductivity and structurally stable net structure to interface with the electrode It can be achieved by providing a stable electrolyte at.

The present invention, in order to achieve the above object, Li, P, X, O and N (wherein the molar ratio (X / P) of X to P is 1 or less and X is B, Si, Al, Ge and As Provided is a solid electrolyte for a five-membered thin-film battery containing five atoms of) selected from the group consisting of.

The invention also forms a target capable of providing Li, P, X and O such that the molar ratio (X / P) of X to P is less than or equal to 1; Li, P, X, O and N, wherein the step of sputtering under an atmosphere containing pure N ₂ or N ₂ to form a thin film containing five elements of Li, P, X, O and N (where , A molar ratio of X to P (X / P) is 1 or less and X is selected from the group consisting of B, Si, Al, Ge and As). to provide.

Hereinafter, the present invention will be described in detail.

The present invention relates to a solid electrolyte for a thin film battery, wherein the solid electrolyte is a five-membered thin film electrolyte containing five atoms of Li, P, X, O and N, and the molar ratio of X to P (X / P) is 1 It is characterized by the following.

The solid electrolyte of the present invention comprises at least two network formers, P and X.

Among the constituent elements of the 5-membered solid thin film electrolyte of the present invention, P and X are substances forming a skeleton of a network, and N is a substance modifying the skeleton of the network to form a net structure.

Examples of the material (X) forming the skeleton of the network include B, Si, Al, Ge, As and the like, which may be supplied by compounds such as B ₂ O ₃ , SiO ₂ , Al ₂ O _3, and the like. . The substance (N) for modifying the skeleton of the network to form a net structure can be supplied by a compound such as Li ₃ N.

According to a preferred embodiment of the present invention there is provided a lithium ion solid electrolyte containing five elements of Li, P, B, O and N and having a molar ratio of B / P of 1 or less. Wherein Li, P, B, O is a substance that forms the skeleton of the network, N is a substance that forms a network structure by modifying the skeleton of the network. In other words, the electrolyte is a Li-P-O and Li-B-O, i.e., a five-membered electrolyte having two network formers and N as a network modifier.

The method for preparing the thin film electrolyte forms a target capable of providing Li, P, X and O such that the molar ratio (X / P) of X to P is 1 or less, and includes pure N ₂ or N ₂ . Performing sputtering in an atmosphere to form a thin film containing five elements of Li, P, X, O and N.

As a target capable of providing Li, P, X and O, a target in which a mosaic target of X or an X-containing compound is positioned on a target of a compound containing Li, P and O may be used. And composite targets containing O elements, but are not limited to these methods. As a composite target containing Li, P, Si, and O, a Li ₃ PO ₄ : Li ₂ SiO ₃ composite target may be used, and as a composite target containing Li, P, B, and O, Li ₃ PO ₄ : LiBO ₂ composite targets may be used.

The electrolyte according to the invention maintains its amorphous form by a low temperature process, whereby high charge carrier concentration, high vacancy or interstitial site concentration, low ion transfer activation energy Has high ionic conductivity. In the electrolyte of the present invention, the B or Si and N materials added to Li-PO contribute to the structural stabilization of the network, thereby improving the bonding strength, bonding properties, relative strength of the bond, and reactivity with lithium ions, thereby improving the structural and chemical properties. It shows stable characteristics. Therefore, the electrolyte may be used for various applications such as micro sensors, medical devices, semiconductor integrated circuits, as well as thin film cells.

Example

Hereinafter, a preferred embodiment of the present invention. However, the following examples are only presented to aid the understanding of the present invention, and the present invention is not limited to the following examples.

Example 1 Preparation of Solid Thin Film Electrolyte

1) Construction of the target

In the composition of Li ₃ PO ₄ powder (Japanese high purity chemistry, purity: 99.5% or more), LiBO ₂ (Aldrich, purity: 98% or more), and x LiBO ₂ ㆍ (1-x) Li ₃ PO ₄ , x is 0.2 After mixing, the mixed powder was heated up to 750 ° C. at a temperature increase rate of 4 ° C./min, and then preheated for 6 hours. Thereafter, it was ground again in a mortar to produce a 2-inch disk. The compressed disk was heated to 750 ° C. at a temperature increase rate of 4 ° C./min, and then heat-treated at this temperature for 4 hours to produce a target having a component of Li-PBO.

b) Fabrication of solid thin film electrolyte

The vacuum in the chamber was evacuated to 2 × ^{0 −6} torr or less, and the exhaust valve was adjusted while flowing N ₂ gas (purity: 99.9999%) at 10 sccm to maintain the vacuum in the chamber of 10 mtorr. At this time, the distance between the target and the substrate was 6 cm. Thereafter, the sputtering power was set to 50 W, the substrate was rotated during sputtering, the substrate was water cooled, and RF sputtering was performed to prepare a thin film electrolyte containing Li-PBON.

Example 2 Impedance Measurement of Thin Film Electrolyte

Impedance measurements were performed to investigate the properties of the solid thin film electrolyte prepared according to Example 1. At this time, the equipment used IM6e of Zahner, Germany, the frequency range was 1MHz ~ 100mHz, and 10mV AC perturbation was applied. Impedance measurements were made in a glove box filled with argon (Ar). The results are shown in Table 1 below.

Target Composition x LiBO ₂ ㆍ (1-x) Li ₃ PO ₄ Sputtering Atmosphere Ionic Conductivity (S / cm @RT ^* ) x = 0.2 Pure N ₂ 6.4 X 10 ^-6

^* RT: room temperature

Example 3: checking the available voltage range

Using the sandwich cell of the Pt / thin film electrolyte / Pt type containing the deposited thin film electrolyte was measured the voltage range that can be used in the battery by a linear sweep voltage method (linear sweep voltage method). The equipment used was Wonatech's charger / discharger, and the current flowing through the cell was measured while increasing the voltage from 0V to 7V at a scan rate of 1 mV / s. 1 is a result of a current-voltage test measurement when x = 0.2 in a target composition of x LiBO ₂ · (1-x) Li ₃ PO ₄ . As can be seen in Figure 1, the thin film electrolyte of the present invention was found to be stable up to about 6V.

In addition, although the above embodiment is described with respect to a thin film electrolyte including Li-BPON, it will be apparent to those skilled in the art that the above embodiment is applied to various network forming agents and modifiers. .

The lithium ion conducting electrolyte of the present invention has excellent stability, low reactivity with the electrode, and stable even with continuous charging and discharging. Due to these physical properties, it can be used in various applications such as thin film cells and micro sensors, which are spotlighted as next generation batteries.

In addition, since the electrolyte of the present invention can be manufactured by applying the thin film deposition technology accumulated in the domestic leading companies, from the foreign currency outflow and the subordination of the technology caused by the existing electrolyte has delivered the manufacturing process, equipment and technology from abroad Because it can escape, it has the advantage of increasing the national interests, the development of the domestic industry, the development of related technologies, and the preoccupation of application fields such as thin film batteries that are being developed around the world.

All simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

1 is a view showing the current-voltage characteristics of the solid thin film electrolyte prepared according to Example 1.

Claims (5)

5 atoms of Li, P, X, O, and N, wherein the molar ratio of X to P (X / P) is 1 or less and X is selected from the group consisting of B. Si, Al, Ge, and As 5-membered solid electrolyte for a lithium secondary battery containing. Forming a target capable of providing Li, P, X, and O such that the molar ratio (X / P) of X to P is 1 or less; Li, P, X, O and N, wherein the sputtering is performed under an atmosphere containing pure N ₂ or N ₂ to form a thin film containing five elements of Li, P, X, O and N (where And a molar ratio (X / P) of X to P is 1 or less, and X is selected from the group consisting of B, Si, Al, Ge, and As). . The target of claim 2, wherein the target capable of providing Li, P, X, and O is a target having a mosaic target of an X or X-containing compound or Li positioned on a target of a compound containing Li, P, and O. 4. A method for producing an electrolyte which is a composite target containing P, X, and O elements.    A lithium secondary battery comprising the electrolyte according to any one of claims 1 to 3.    Micro sensor comprising an electrolyte according to any one of claims 1 to 3.