DE202022103923U1 - solid electrolyte structure - Google Patents

Abstract

A solid electrolyte structure comprising a solid electrolyte particle which is a titanium-containing solid electrolyte; and a protective layer completely covering the solid electrolyte particle, thereby preventing the reduction reaction of titanium in the solid electrolyte particle and improving the electrochemical durability of the solid electrolyte particle.

Description

field of invention

The present invention relates to a solid electrolyte structure, and more particularly to a titanium-containing solid electrolyte structure having a protective layer.

State of the art

For existing lithium-ion secondary batteries, liquid electrolytes are mainly used as lithium-ion transport media. However, the volatility property of electrolytes has adverse effects on the human body and the environment. At the same time, the flammability of liquid electrolytes also poses a major safety concern for battery users.

At present, one of the reasons for the unstable performance of lithium batteries is mainly due to the large surface activity of an electrode (negative electrode) and high voltage (positive electrode). When an electrode comes into direct contact with an electrolytic solution, the interface between the two becomes unstable, causing a so-called exothermic reaction and thereby forming a passive protective film on the contact interface. These reactions consume liquid electrolytes and lithium ions while also generating heat. As soon as a local short circuit occurs, the local temperature rises rapidly. At this time, the passive protection film becomes unstable, and at the same time, heat is released. This exothermic reaction increases, so that the temperature of the battery continues to rise. Once the battery temperature rises to the thermal runaway initial temperature (or trigger temperature, thermal runaway), it will cause a thermal runaway, resulting in battery damage such as battery failure. B. explosion or fire, and thus significant safety concerns in use exist.

Solid electrolytes have become an important research focus in recent years. They exhibit ionic conductivity similar to liquid electrolytes but do not have the volatility and flammability properties of liquid electrolytes. At the same time, their interface with the surface of an active material is relatively stable (both chemically and electrochemically). However, solid electrolytes differ from liquid electrolytes in that they have small and poor contact areas with active materials and a low charge transfer reaction constant. Therefore, there is a problem that in the solid electrolyte, the resistance value of the interface of the positive and negative electrodes of the electrode layer with an active material in charge transfer is relatively large, which is not conducive to the efficient transport of lithium ions. Therefore, it is still difficult to completely replace liquid electrolytes.

In addition, compared to liquid electrolytes, the material costs themselves are significantly higher for solid electrolytes. In order to reduce costs and to control and improve the compatibility of the material, various materials have been developed in recent years. Among them, the lithium-aluminum-titanium-phosphate (LATP)-based solid electrolyte, for example, offers significant cost advantages in addition to good ionic conductivity. However, the electrochemical stability of the lithium aluminum titanium phosphate (LATP) based solid electrolyte at low voltage is poor due to its titanium content. During deposition, it reacts with lithium (ions), contaminating the negative electrode layer and affecting the normal performance of the electrochemical reaction. Therefore, it is difficult to expand its application range.

How to effectively and widely use a solid electrolyte while also considering the cost and improvement of the surface condition of the solid electrolyte is an urgent problem to be solved in this field.

object of the invention

The object of the invention is to avoid the above-mentioned disadvantages of the prior art and to provide a solid electrolyte structure which not only has relatively low material costs but can also be applied to all electrode layers without restriction.

Another object of the present invention is to provide a solid electrolytic structure capable of preventing the deposition of internal titanium by providing a protective layer and further avoiding various problems such as e.g. B. a high charge transfer resistance and a small contact area caused by the contact area of the solid electrolyte can be solved.

To achieve the above objects, the present invention provides a solid electrolyte structure comprising a solid electrolyte particle and a protective layer, wherein the solid electrolyte particle is a titanium-containing solid electrolyte and is completely encased by the protective layer in order to prevent the solid electrolyte particle from To prevent the reduction reaction of titanium, to improve the electrochemical resistance at low voltage, to effectively prevent contamination of the electrode layer caused by titanium, and thus to expand the application range of titanium-containing solid electrolytes.

Here, the protective layer can consist of a solid metal oxide, a polymer or a combination thereof. By arranging the protective layer, reduction of titanium in the solid electrolyte particle can be effectively prevented and electrochemical durability at low voltage can be improved. With regard to the outside of the solid electrolyte particles, the arrangement of the protective layer can effectively solve the problems caused by the high charge transfer resistance and the small contact area, and thus can achieve optimal ion conduction, while also considering the cost and safety Find.

For a better understanding of the objects, technical features, contents and advantageous effects of the present invention, a specific embodiment will be described in detail below with reference to the accompanying drawings.

character list

• 1 shows a schematic view of the embodiment of the solid electrolyte structure according to the invention;
• 2 12 is a graph of the distribution curve of the concentration of titanium according to the embodiment of the solid electrolyte structure of the present invention.

Detailed description of the embodiment

1 shows a schematic view of the embodiment of the solid electrolyte structure according to the invention. The solid electrolyte structure 10 according to the invention consists primarily of a solid electrolyte particle 11 and a protective layer 12. The solid electrolyte particle 11 is a titanium-containing solid electrolyte, such as. B. a lithium aluminum titanium phosphate (LATP; Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ ) based solid electrolyte and has a fairly high ionic conductivity, good chemical and thermal stability and at the same time low material and manufacturing costs. Therefore, it has received a lot of attention in recent years. However, its chemical resistance is not good because when titanium is deposited (especially at low voltage), its surface properties are changed and thus the ionic conductivity of the surface is reduced, and because the interfacial resistance is greatly increased due to the reaction of titanium with lithium(ions) and thus the properties and efficiency of electrochemical reactions are severely impaired.

In view of this, in the present invention, the solid electrolyte particle 11 is completely covered by the protective layer 12 in order to prevent the solid electrolyte particle 11 from precipitating titanium. The protective layer 12 has a thickness of 10 to 500 nm and encases the surface of the solid electrolyte particles 11 completely. It should be noted here that the state of the solid electrolyte particles 11 shown in the figure is for illustration only, and their shape is not limited to a round shape (sphere). Other spheroids, disk shapes, or plate shapes can also be used for them.

After the solid electrolyte particles 11 have been encased by the protective layer 12, they must still have a certain degree of ionic conductivity and good chemical and thermal stability. Therefore, in terms of material selection, a solid metal oxide, an organic polymer, or a combination thereof can be used. As the manufacturing method, sintering, soaking, coating, etc. can be used, but the present invention is not limited in this respect. In addition to the above-mentioned LATP, the solid electrolyte particles 11 may also be various titanium-containing oxide-based solid electrolytes such as Li _1+x+y (Al,Ga) _x (Ti,Ge) _2-x Si _y P _3-y crystals O ₁₂ where 0 ≤ x ≤ 1 and 0 ≤ y ≤ 1, Li ₂ O-Al ₂ O ₃ -SiO ₂ -P ₂ O ₅ -TiO ₂ , Li ₂ O-Al ₂ O ₃ -SiO ₂ -P ₂ O ₅ -TiO ₂ -GeO ₂ , Li _3x La _2/3x TiO ₃ , Li _0.38 La _0.56 Ti _0.99 Al _0.01 O ₃ and Li _0.34 LaTiO _2.94 .

It will be on 2 referenced. If the surface of the solid electrolyte particles 11 is provided with the protective layer 12, it can be clearly seen that the deposition of titanium (usually an ionic deposition) is completely prevented due to the hindrance by the protective layer 12 and only within the solid electrolyte particles 11 done. Therefore, with respect to the solid electrolyte particles 11, the main function and purpose of the protective layer 12 is to prevent the precipitation of titanium from the solid electrolyte structure 10.

In particular, when the protective layer 12 is a solid metal oxide, the thickness is preferably about 10 to 50 nm. The protective layer can be, for example, a niobium oxide (NbO _x ) and a derivative thereof such as niobium trioxide (Nb ₂ O ₃ ) or a lithium nitrate (LiNO _x ) and be a derivative thereof. Furthermore, the protective layer 12 can also be a solid electrolyte based on lithium lanthanum zirconium oxide (Li ₇ La ₃ Zr ₂ O ₁₂ ; LLZO). Although LLZO has a relatively stable chemical resistance and excellent ion conductivity capability and chemical and thermal stability, but its material and manufacturing costs are relatively high. Because a protective layer 12 is formed on the surface of the titanium-containing solid electrolyte particles 11 (such as LATP) through the use of LLZO, not only can the costs be greatly reduced during use, but at the same time the chemical resistance of the solid electrolyte structure 10 due to the relatively stable interface of LLZO, which significantly expands the range of applications.

When the protective layer 12 is a polymer, the thickness is preferably about 20 to 500 nm, the protective layer being made of an ion-conductive polymer material or a polymer-based solid electrolyte. For example, when the protective layer 12 is made of an ion-conductive polymer material, it can be selected from the following materials: polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polypotassium methacrylate (PMMA) and polyvinylidene chloride (PVC). Furthermore, it can be modified by adding a film former (e.g. a crosslinked film-forming material) and a plasticizer to further improve its film formation. After the addition of the film former, the plasticizer can remain or be removed (this can only be added during the film formation process and removed after film formation). The plasticizer can be selected from the following materials: propylene carbonate (PC), ethylene carbonate (EC), dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

In another embodiment, the protective layer 12 is composed of an ionically conductive polymeric material to which is added a film former (e.g., a crosslinked film-forming material) and an ionic liquid. If such a solid polymer electrolyte is used for the protective layer 12 and the solid electrolyte particle 11 is covered by the protective layer, in addition to preventing the precipitation of titanium from the solid electrolyte particle 11, the state of the contact interface between the solid electrolyte particles 11 or between a Solid electrolyte particles 11 and an active material can be greatly improved because of the soft texture of the solid polymer electrolyte, effectively solving the problems caused by high charge transfer resistance and small contact area, and thus achieving optimal ion conduction while also reducing costs and safety are taken into account.

In the above embodiment, in which the protective layer 12 is made of an ion-conductive polymer material, an ion donor material such as salt may be added to increase ion conductivity and form a polymer-based solid electrolyte. Alternatively, the solid electrolyte consists of an ion-conducting material, a film former and an ion donor material.

In summary, the following effects can be achieved in the solid electrolyte structure according to the invention by the arrangement of the protective layer: With regard to the inside of the solid electrolyte particles, the arrangement can effectively prevent the precipitation of titanium and improve the chemical resistance; With regard to the outside of the solid electrolyte particles, the arrangement of the protective layer can effectively solve the problems caused by the high charge transfer resistance and the small contact area, and thus can achieve optimal ion conduction, while also considering the cost and safety Find.

The foregoing description represents only a preferred embodiment of the invention and is not intended to limit the scope of the present invention. All equivalent changes and modifications, which can be made by one skilled in the art in accordance with the description and drawings of the invention, fall within the scope of the present invention.

Reference List

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solid electrolyte structure

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solid electrolyte particles

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protective layer

Claims (14)

A solid electrolyte structure comprising a solid electrolyte particle which is a titanium-containing solid electrolyte; and a protective layer completely covering the solid electrolyte particle, thereby preventing the reduction reaction of titanium in the solid electrolyte particle and improving the electrochemical durability of the solid electrolyte particle. solid electrolyte structure claim 1 , in which the solid electrolyte particle is a lithium aluminum titanium phosphate (LATP) based solid electrolyte. solid electrolyte structure claim 1 , in which the thickness of the protective layer is 50 to 500 nm. solid electrolyte structure claim 1 wherein the protective layer material is a solid metal oxide, a polymer, or a combination thereof. solid electrolyte structure claim 4 , wherein the solid metal oxide is a niobium trioxide (Nb ₂ O ₃ ) or a derivative thereof. solid electrolyte structure claim 4 , in which the solid metal oxide is a lithium nitrate (LiNO _x ) or a derivative thereof. solid electrolyte structure claim 4 , wherein the solid metal oxide is a lithium lanthanum zirconia (Li ₇ La ₃ Zr ₂ O ₁₂ ; LLZO) based solid electrolyte. solid electrolyte structure claim 4 , in which the polymer mainly consists of an ionically conductive material. solid electrolyte structure claim 8 , in which the ionically conductive material is selected from the following materials: polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polypotassium methacrylate (PMMA) and polyvinylidene chloride (PVC). solid electrolyte structure claim 8 , in which the material of the protective layer comprises a film former. solid electrolyte structure claim 10 , in which the material of the protective layer comprises a plasticizer. solid electrolyte structure claim 10 , in which the material of the protective layer comprises an ionic liquid. solid electrolyte structure claim 10 , 11 and 12 , wherein the material of the protective layer comprises an ion donor material. solid electrolyte structure Claim 13 , in which the ion donor material is a salt.

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