KR101569367B1 - Highly ion conductive glass ceramics for Li ion secondary cell - Google Patents

Abstract

The present invention relates to a high ion conductive glass ceramic for a lithium ion secondary battery and a process for producing the same, and more particularly, to a process for producing a multi-layered electrolyte for a lithium ion secondary battery comprising a cathode and an anode capable of intercalating / deintercalating lithium ions .
As described above, according to the present invention, it is possible to provide a glass ceramic for a lithium ion secondary battery which is excellent in ionic conductivity, improves the charge / discharge cycle characteristics of the battery, improves the charge / discharge capacity of the battery, , Especially a solid electrolyte, can be expected.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a high-ion conductive glass ceramics for a lithium ion secondary battery,

The present invention relates to a high ion conductive glass ceramic for a lithium ion secondary battery and a method for producing the same, and more particularly, to a process for producing a multi-layered electrolyte for a lithium ion secondary battery including a positive electrode and a negative electrode capable of inserting / .

A battery is a device that converts chemical energy into electrical energy by electrochemical oxidation and reduction reactions, and can be classified into a chemical cell and a physical cell. Chemical cells are classified into primary cells, secondary cells, and fuel cells, and physical cells are classified into solar cells, thermoelectric elements, and nuclear power cells.

Secondary cells are the most widely used batteries at present, and in particular, lithium ion secondary batteries are cells that can be repeatedly charged and discharged because the mutual conversion between chemical energy and electric energy is reversible. Reuse is the most important feature.

Lithium secondary batteries have recently developed remarkably and are being applied not only to mobile devices such as mobile phones and notebooks but also to automobiles and transportation devices requiring large capacity and also to store high-output electricity generated for power generation associated with solar cells or wind cells And is also used as a power storage device.

Various batteries capable of overcoming the limitations of current lithium secondary batteries have been studied from the viewpoints of capacity, stability, output, large size, and small size of cells represented by high energy density for various applications. Here, a large-sized battery is a battery capable of charging a large amount of electricity generated from a system such as a wind power or NAS battery in a battery. In this case, the amount of electricity supplied during charging is not constant, The performance of the battery should not be deteriorated or the battery should not be inflated or exploded. In contrast to the ultra-small cell phone, the cell phone and the flip-chip mobile phone have high capacity and high output.

Currently, the battery to be developed has an average operating time three times that of conventional batteries, so the stored energy is as high as that. However, securing the stability of the battery is a very important task, because active materials having high activity generating high energy and non-aqueous organic electrolytes having combustibility are in contact with each other in the same space. Therefore, in the aspect of stability, ultimately, all solid-state batteries are being pursued. Particularly, studies on solid electrolytes, which are core technologies of all solid-state batteries, are actively conducted mainly in Japan.

The solid electrolyte means a material capable of diffusing lithium ions at a high speed in a solid interior. Particularly, a solid electrolyte having a high ionic conductivity and excellent electrochemical stability has been studied. These solid electrolytes are manufactured using materials of various properties and shapes such as crystalline, amorphous (glass), polymer, and composite, and development of all solid batteries using such solid electrolytes is also progressed .

In general, the inorganic solid electrolyte can be classified into a sulfide system and an oxide system. The solid electrolyte having the most advanced technology development is a sulfide solid electrolyte. The solid electrolyte has an ion conductivity of 10 ^-3 S / cm and is close to the organic electrolyte Ion conductivity. However, in the sulfide-based solid electrolyte, the interface resistance between the electrode active material and the solid electrolyte is higher than that of the organic electrolyte, and hydrogen sulfide (H ₂ S) is generated by reaction with water.

The oxide-based solid electrolytes include crystalline and amorphous solid electrolytes, and crystalline solid electrolytes have lattice defects and have a high ion conductivity by forming a passage through which lithium ions can move. However, such a solid electrolyte is disadvantageous in that ion conductivity is decreased due to grain boundary resistance of grain boundaries due to crystallinity. In addition, since a high temperature heat treatment is required for crystallization, there is a disadvantage in that the composition selection limitations and the electrode / electrolyte interface properties are lowered and the electron conductivity is reduced by the reduction of the transition metal.

The amorphous oxide solid electrolyte has a property of high ion conductivity because it has a wide space in which lithium ions can move. The oxide-based phosphate compound series exhibits high ionic conductivity and can be made into a crystallized glass state unlike other oxide-based solid electrolytes. The solid electrolyte of the phosphate compound series formed in the crystallized glass state can have a high ionic conductivity because it exists between the particles and the particles in the form of glass and can reduce the resistance between the particles.

At present, the biggest problem in studying solid electrolytes is that ion conductivity is lower than that of sulfide-based electrolytes.

SUMMARY OF THE INVENTION The present invention has been conceived to solve the above problems, and an object of the present invention is to provide an electrolyte for a lithium ion secondary battery having excellent ion conductivity and simple manufacturing method.

Particularly, the present invention relates to a solid electrolyte and a lithium ion secondary battery having such a solid electrolyte, which do not use an electrolyte solution, have a high battery capacity and good charge-discharge cycle characteristics, can be used stably for a long period of time, And a solid electrolyte which is easy to handle.

In order to achieve the above object, the present invention provides a high ion conductive glass ceramic for a lithium ion secondary battery, wherein the glass ceramics is Li _{1 .2 + x} Ti _{2 - x} Al _{0 .5} (PO 4) ₃ The present invention provides high ion conductive glass ceramics for lithium ion secondary batteries.

The glass ceramics are preferably solid electrolytes.

It is preferable that the thickness of the solid electrolyte after sintering is 10 탆 to 0.5 mm.

Further, the present invention relates to a method for manufacturing a semiconductor device, comprising: weighing and mixing an oxide or a salt containing Li, Ti, Al and P as a component to satisfy the following equation; Cooling and pulverizing the mixed component after melting to produce a pulverized product; And forming and sintering the pulverized product. The present invention also provides a method for manufacturing a high ion conductive glass ceramic for a lithium ion secondary battery.

[expression]

Li _{1 .2 + x} Ti _{2 - x} Al _{0 .5} (PO 4) ₃ ( _{0 ? X} ? 0.4)

The melting temperature of the mixed component is preferably 1300 ° C to 1500 ° C in the step of melting, cooling, and pulverizing to produce a pulverized product.

In the step of melting and then cooling and pulverizing the mixed component to produce a pulverized product, it is preferable that the heating rate and cooling rate at the time of melting are 100 to 300 ° C / hr.

In the step of forming and sintering the pulverized product, the sintering temperature is preferably 1000 ° C to 1250 ° C.

The glass ceramics are preferably solid electrolytes.

As described above, according to the present invention, it is possible to provide a glass ceramic for a lithium ion secondary battery which is excellent in ionic conductivity, improves the charge / discharge cycle characteristics of the battery, improves the charge / discharge capacity of the battery, In particular, a functional effect of producing a solid electrolyte is expected.

In addition, it is possible to produce glass ceramics for a lithium ion secondary battery by a conventional melting process without a reheat process, which is easy to manufacture and handle industrially and can reduce manufacturing cost.

1 is a schematic view and a photograph showing a lithium dendrite structure of a lithium ion battery.
2 is an X-ray graph according to the x composition of the solid electrolyte produced by the embodiment of the present invention.
3 is a photograph of a solid electrolyte produced by sintering at 1200 DEG C according to an embodiment of the present invention.
4 is a graph of electrical conductivity according to the x composition of the solid electrolyte produced by the embodiment of the present invention.
5 is a graph showing the ionic conductivity of the amorphous solid electrolyte shown as a comparative example.

Hereinafter, the present invention will be described in more detail based on the accompanying drawings and preferred embodiments.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In describing the present invention, the defined terms are defined in consideration of the functions of the present invention, and they may be changed according to the intention or custom of the technician working in the field, and the definition is based on the contents throughout this specification It should be reduced.

Conventionally, the solid electrolyte is a sulfide system. In an aqueous process method in which water is used in preparing an electrode active material sheet in a current battery manufacturing process, the electrolyte reacts with water to generate hydrogen sulfide (H ₂ S). Also, even in the case of the oil-phase process, the humidity control of the entire process is necessarily required. Furthermore, since the sulfide-based solid electrolyte must be shielded from contact with air even when it is molten, the process is complicated and difficult.

On the other hand, oxide-based solid electrolytes are advantageous in that all the processes are performed in air, and in particular, the water-based process is also suitable for the battery manufacturing process.

All solid-state batteries employing solid electrolytes are cells that replace the liquid electrolyte used in conventional lithium secondary batteries with solid materials, and have greatly improved safety because no ignition or explosion occurs due to the decomposition reaction of the electrolyte.

When the electrolyte is used as a solid, it has advantages such as (1) improved stability, (2) a battery having an optimized structure, (3) a high energy density, and (4) a high output density as compared with a battery using an electrolyte solution.

In particular, Li-metal or Li-alloy, which has a very large capacity, can be used as an anode material. Therefore, the energy density of the battery mass and volume is 8 to 10 times larger than that of graphite or carbon. A battery having improved performance can be manufactured.

When a liquid electrolyte and an organic separator are actually used, during the charge / discharge cycle, as shown in FIG. 1, Li ions grow from the negative electrode active material into a finger shape or lithium grows into a dendrite phase (tree branch) Eventually, both electrodes are short-circuited and can not be used as a risk of explosion. Therefore, in order to produce a battery having a high capacity, a high density and a high output, a solid electrolyte using a solid electrolyte is indispensable.

Furthermore, when a solid electrolyte is applied, various types of high capacity batteries can be manufactured by manufacturing a stacked battery or a segmented type battery in which a plurality of cells are stacked, and studies have been started in the United States and Japan.

The glass ceramics produced by the present invention can be made of solid electrolytes as applications, and such solid electrolytes can be used in large-capacity power storage devices for automobiles and power generation systems requiring safety, high capacity and high output, or Li / Zn batteries, redox flow cells, and Li / Mn batteries. It does not limit other uses.

The glass ceramics according to the present invention are characterized by being non-sulfide based.

The glass ceramics according to the present invention can be used as a solid electrolyte for a lithium ion secondary battery and expressed by a composition formula such as Li _{1 .2 + x} Ti _{2 - x} Al _{0 .5} (PO ₄ ) ₃ ( _{0 ≦ x ≦} 0.4).

If the range of x in the above composition is more than 0.4, a secondary phase such as AlPO ₄ is produced and the crystallinity of LiTi ₂ (PO ₄ ) _{3, which} is the main crystal phase of the crystallized glass, is lowered, resulting in low ion conductivity. Thus, the above composition has a critical significance in the above range.

Here, it is preferable that the thickness of the solid electrolyte after sintering is 10 탆 to 0.5 mm. The thinner the electrolyte is, the better the ionic conductivity. If the electrolyte is too thin, it does not have the strength, and if the battery is manufactured by stacking the thick film in multiple layers, there is a complex process. That is, the above numerical range has a critical significance in order to secure a certain strength or higher while having a proper ion conductivity.

<Production Example>

Meanwhile, the present invention can produce a solid electrolyte by the following production method.

1. Selection of raw materials

First, an oxide or a salt containing Li, Ti, Al and P as components is weighed and mixed so as to satisfy Li _{1.2 + x} Ti _2-x Al _0.5 (PO ₄ ) ₃ (0? _X ? 0.4) .
The process of weighing in this way is described as follows.
x Li2CO3 TiO2 Al2O3 P2O5 0 0.6 1.8 0.25 1.5 0.1 0.65 1.7 0.25 1.5 0.2 0.7 1.6 0.25 1.5 0.3 0.75 1.5 0.25 1.5 0.4 0.8 1.4 0.25 1.5 Molecular Weight 73.891 79.866 101.977 141.945 x The 0 Li1.2Ti1.8Al0.5 (PO4) 3 0.1 Li1.3Ti1.7Al0.5 (PO4) 3 0.2 Li1.4Ti1.6Al0.5 (PO4) 3 0.3 Li1.5Ti1.5Al0.5 (PO4) 3 0.4 Li1.6Ti1.4Al0.5 (PO4) 3
For example, when x is 0.1, the given molar value of each element of the formula Li, Ti, Al, and P is 1.3, Ti is 1.7, Al is 0.5, and P is 3 when x is 0.1. That is, Li: Ti: Al: P = 1.3: 1.7: 0.5: 3.
Meanwhile, the number of moles in the oxides of the starting material (in the case of Li salt of the Li ₂ CO ₃₎ form is, Li is 2 (Li ₂ because CO _3), Ti is 1 (because TiO _2), Al is 2 (Al ₂ O ₃ ), and P becomes 2 (since it is P ₂ O ₅ ).
Therefore, Li ₂ CO ₃ of the starting material is required to be charged as much as 0.65, which is the number of moles corresponding to half of Li, to satisfy Li = 1.3, and other elements can be calculated by the same method.
The calculation method of the amount of each element is a known calculation method according to the rules of general chemistry.
On the other hand, calculation of the weight ratio is required for weighing, and the weight according to each molar value is calculated using the converted molar value of each starting material and the molecular weight of the starting material as shown in the following table.
(Unit: weight) x Li2CO3 TiO2 Al2O3 P2O5 total 0 44.3346 143.7588 25.4943 212.9175 426.5052 0.1 48.0292 135.7722 25.4943 212.9175 422.2131 0.2 51.7237 127.7856 25.4943 212.9175 417.9211 0.3 55.4183 119.7990 25.4943 212.9175 413.6290 0.4 59.1128 111.8124 25.4943 212.9175 409.3370
As for the method of calculating the weight as above, it is said that the molecular weight shown in Table 1 is multiplied by the corresponding molar value, and this also corresponds to the known theory of general chemistry.
The following examples were carried out on the basis of the weight ratios calculated as above.

On the other hand, the critical meaning of x is as described above. According to an embodiment of the present invention, among the oxides or salts, Li ₂ CO ₃ , TiO ₂ , Al ₂ O ₃ and P ₂ O ₅ are selected. That is, Li is a salt, and Ti, Al, and P are oxides, and the reasons for choosing them are not special, but they are easy to obtain and cheap. Here, the purity of the above materials was 99% or more.

2. Melting step

The mixed starting materials were accommodated in an alumina crucible and melted, and then the process of cooling the amorphous materials was controlled.

According to an embodiment of the present invention, the melting temperature range is from 1300 ° C to 1500 ° C. When the temperature is lower than 1300 ° C, the melt is not melted. When the temperature exceeds 1500 ° C, a secondary phase is formed, The range has its critical significance.

Here, it is preferable that the heating rate and the cooling rate at the time of melting are 200 ° C / hr. However, the available range may be set at 100 to 300 ° C / hr. In this case, when the temperature is lower than 100 ° C and the cooling is carried out, there is no influence on the crystallinity and crystallinity, but a lot of electricity is consumed. When the temperature is higher than 300 ° C, There is a problem of losing, so the above numerical range has its critical significance.

3. Grinding and molding steps

The thus-prepared melt was placed in an alumina pot, pulverized with a ball mill for 24 hours using ethanol and alumina balls, and then dried at 80 DEG C for 24 hours to prepare a powder. Thereafter, this is molded by a uniaxial pressing method, thereby realizing an approximate shape of a solid electrolyte.

Here, the operating time, drying time, and drying temperature of the upper ball mill are simply optimized, and it is not excluded that they are performed under different conditions.

4. Sintering step

The molten material thus formed was sintered to prepare a solid electrolyte.

At this time, the sintering temperature is preferably 1000 deg. C to 1250 deg. Here, when the temperature is less than 1000 ° C, the sintering is not performed because the temperature is low, and when the temperature exceeds 1250 ° C, re-melting may occur, so that the above numerical range has its critical significance.

The method of manufacturing a solid electrolyte realized through such steps is characterized by a manufacturing process without a reheat process after the melting of the raw material. In the case of producing a solid electrolyte using glass, all the sulfide-based and oxide-based materials are melted and rapidly quenched to produce glass. The glass thus produced is crushed and crystals are produced at a constant temperature to produce a crystallized glass. However, in the present invention, the crystallization glass can be produced by adjusting the cooling rate without additional rapid cooling during melting, which has been experimentally confirmed. Therefore, the present invention is characterized by a simplified process as long as the quenching process is omitted.

2 is an X-ray graph according to the x composition of the solid electrolyte produced by the embodiment of the present invention.

As shown in the figure, no phase other than the composition of LiTi ₂ (PO ₄ ) ₃ was found in the composition range proposed in the present invention, and therefore crystals having high crystallinity were generated. can confirm.

3 is a photograph of a solid electrolyte produced by sintering at 1200 DEG C according to an embodiment of the present invention.

As shown in the drawing, a dense solid electrolyte having a thickness of 0.1 mm could be produced by sintering at 1200 ° C for 2 hours using the composition of the present invention.

4 is a graph of ion conductivity according to x composition of a solid electrolyte produced by an embodiment of the present invention.

As shown in the figure, the ion conductivity was measured from 25 ° C to 300 ° C, and as a result, a solid electrolyte having an excellent ionic conductivity of about 10 ^-3 S / cm could be produced in this range.

As a comparative example, the ionic conductivity measured in an oxide amorphous solid electrolyte as a conventional amorphous solid electrolyte is shown in FIG.

FIG. 5 is a graph showing the results of the thermoanalytical, structural and ionic conductivity studies on 50Li2O-45P2O5-5Nb2O5 glass (Prashant Dabas, K. Hariharan) published at the 2012 Solid State Ionics About 3.4. As can be seen from the graph above, it can be seen that the ion conductivity is high when it is raised at a high temperature. It can be seen that the composition according to the present invention exhibits a higher ionic conductivity than the above comparative example.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (8)

In high ion conductive glass ceramics for lithium ion secondary batteries,
_Wherein said glass ceramics has a composition formula of Li _{1 .2 + x} Ti _{2 - x} Al _{0 .5} (PO ₄ ) ₃ ( _{0 ? X} ? 0.4). The method according to claim 1,
Wherein said glass ceramics are solid electrolytes. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; 3. The method of claim 2,
Wherein the solid electrolyte has a thickness of 10 탆 to 0.5 탆 after sintering. Weighing and mixing an oxide or a salt containing Li, Ti, Al and P as a component to satisfy the following equation;
Cooling and pulverizing the mixed component after melting to produce a pulverized product;
Molding and sintering the pulverized product;
The method for manufacturing a high ion conductive glass ceramics for a lithium ion secondary battery according to claim 1,
[expression]
Li _{1 .2 + x} Ti _{2 - x} Al _{0 .5} (PO ₄ ) ₃ ( _{0 ? X} ? 0.4) 5. The method of claim 4,
Wherein the melting temperature of the mixed component is from 1300 ° C to 1500 ° C in the step of melting, cooling, and pulverizing the mixed component to produce a pulverized product. 5. The method of claim 4,
Wherein the molten mixture is cooled and pulverized to produce a pulverized product, wherein the heating rate and the cooling rate at the time of melting are 100 to 300 ° C / hr, respectively, and the production method of the high ion conductive glass ceramics for lithium ion secondary batteries . 5. The method of claim 4,
Wherein the sintering temperature is in the range of 1000 ° C. to 1250 ° C. in the step of molding and sintering the pulverized product. 5. The method of claim 4,
Wherein the glass ceramics is a solid electrolyte. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;

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