A method of enhancing the binding of solid-state battery electrolyte and electrode interfaces

Abstract

This invention relates to the field of solid-state battery technology, specifically to a method for enhancing the bonding between the electrolyte and electrode interface in a solid-state battery. It includes the following steps: S1, mixing SiO2 with an alkali metal oxide to form a transition layer material, wherein the alkali metal oxide includes one or more of Li2O, Na2O, and K2O; S2, uniformly mixing the transition layer material and then sintering it at high temperature, followed by water quenching; S3, ball milling the transition layer material; S4, spraying the transition layer material onto the surface of the negative electrode material and the ceramic electrolyte using wet cold gas spraying or electrostatic powder spraying; S5, after the sprayed transition layer material dries, bonding the negative electrode material and the ceramic electrolyte together, and then sintering at high temperature to form a transition coating. Compared to traditional solid-solid interface contact, this invention has the advantages of better bonding effect and lower interface impedance, and also provides a channel for rapid lithium-ion transport.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, and in particular to a method for enhancing the bonding between the electrolyte and electrode interface in solid-state batteries. Background Technology

[0002] Anode materials directly affect the main performance characteristics of lithium batteries, such as capacity, initial efficiency, and cycle life. The development path of solid-state batteries, "low silicon - high silicon - lithium metal," has been widely recognized in the industry. Lithium metal anode batteries, with their ultra-high theoretical specific capacity and extremely high energy density, have become the long-term iterative direction for anode materials. Among numerous solid electrolyte materials, garnet-type lithium lanthanum zirconium oxide (Li7La3Zr2O) stands out. 12 Ceramic oxide solid electrolytes, represented by LLZO, exhibit excellent chemical stability to lithium, with a stability greater than 10. -3 Its advantages, such as room-temperature lithium-ion conductivity (dense LLZO ceramic electrolyte, relative density >99.6%), extremely high shear modulus (56-61 GPa, more than 7 times that of metallic lithium), and wide electrochemical window, make it one of the most promising solid-state electrolyte materials for application.

[0003] If solid-state batteries use lithium metal and alloys as negative electrode materials and LLZO as electrolyte, their safety and energy density will be significantly improved. However, the current interface between metal electrodes and ceramic oxide electrolytes has prominent problems such as poor contact between metal and ceramic, mismatch of thermal expansion coefficients, and lithium dendrites. These problems can lead to reduced lithium-ion transport efficiency, increased impedance, and affect battery performance. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the background art by proposing a method to enhance the bonding between the electrolyte and electrode interface in solid-state batteries.

[0005] The technical solution of the present invention provides a method for enhancing the bonding between the electrolyte and electrode interface in a solid-state battery, comprising the following steps: S1. SiO2 is mixed with alkali metal oxides to form a transition layer material, wherein the alkali metal oxides include one or more of Li2O, Na2O and K2O; S2. The transition layer raw materials are uniformly mixed and then sintered at high temperature, followed by water quenching. S3. The transition layer material is ball-milled. S4. The transition layer material is sprayed onto the surface of the negative electrode material and the ceramic electrolyte using wet cold gas dynamic spraying or powder electrostatic spraying. S5. After the raw material of the transition layer to be sprayed is dried, the negative electrode material and the ceramic electrolyte are bonded together, and then sintered at high temperature to form the transition coating.

[0006] Preferably, the negative electrode material is an AlLi alloy, and the ceramic electrolyte is Li7La3Zr2O. 12 .

[0007] Preferably, in the formulation of the transition layer raw materials, the SiO2 content is 60%-90% and the alkali metal oxide content is 10%-40%.

[0008] Preferably, the transition layer raw materials are sintered at a high temperature of 1350-1400℃ for 30 minutes after mixing; the transition layer raw materials after spraying and bonding are sintered at a high temperature of 500-550℃ for 10-15 minutes.

[0009] Preferably, the coating thickness of the transition layer material is 5-20 μm.

[0010] Preferably, the particle size of the transition layer material after ball milling is ≤200 mesh.

[0011] Preferably, AlLi alloy nanopowder is added to the transition coating to form a gradient transition coating, in which the content of AlLi alloy nanopowder gradually decreases from the side closer to the negative electrode material to the other side.

[0012] Preferably, ceramic electrolyte powder is added to the transition coating to form a gradient transition coating in which the content of ceramic electrolyte powder gradually decreases from the side closer to the ceramic electrolyte to the other side.

[0013] Preferably, AlLi alloy nanopowder and ceramic electrolyte powder are added to the transition coating to form a gradient transition coating. In this gradient transition coating, the content of AlLi alloy nanopowder gradually decreases from the side closer to the negative electrode material to the other side, and the content of ceramic electrolyte powder gradually decreases from the side closer to the ceramic electrolyte to the other side.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: 1. This invention designs a transition coating between the electrode and the electrolyte. The transition coating is mainly formed by mixing SiO2 and alkali metal oxides. SiO2 is the main component of the amorphous network skeleton, while Li+ / Na+ / K+ in the alkali metal oxides play a role in breaking the network skeleton, thereby promoting the formation of non-bridged oxygen bonds and atomic vacancies in the Si-O network. This allows relevant atoms in the negative electrode material and ceramic electrolyte material to diffuse into the vacancies in the intermediate layer during sintering, ultimately forming a "you in me, me in you" structure at the interface. Compared with the traditional solid-solid interface contact, this chemical metallurgical bonding has a better bonding effect and lower interface impedance. 2. The multilayer gradient transition layer design proposed in this invention forms a smooth transition zone between the electrode and the electrolyte by adjusting the distribution of AlLi nanopowder or ceramic electrolyte powder in the transition coating. The gradient design can effectively avoid stress concentration on a single interface and also solves the problem of interface peeling caused by volume expansion effect. 3. The transition coating in this invention forms a fast transport channel for lithium ions, and the alkali metal ions and network structure in the coating itself also have the ability to store lithium ions, which can serve as additional active sites to provide a certain capacity, thereby improving the overall energy density of the battery. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the interfacial bonding reaction process in this invention; Figure 2 This is a schematic diagram of the preparation process in this invention; Figure 3 This is a schematic diagram of the gradient transition layer of the AlLi alloy anode material in this invention; Figure 4 This is a schematic diagram of the gradient transition layer of the ceramic electrolyte material in this invention; Figure 5 This is a schematic diagram of the dual-gradient transition layer of AlLi alloy anode material and ceramic electrolyte material in this invention. Detailed Implementation

[0016] Example 1 like Figure 1 and Figure 2 As shown in the figure, this embodiment proposes a method for enhancing the bonding between the electrolyte and electrode interface in a solid-state battery, comprising the following steps: S1. SiO2 is mixed with alkali metal oxides to form a transition layer material, wherein the alkali metal oxides include one or more of Li2O, Na2O, and K2O; in the ratio of the transition layer material, the content of SiO2 is 60%-90%; and the content of alkali metal oxides is 10%-40%. S2. After uniformly mixing the transition layer raw materials, sinter them at high temperature. After mixing, the transition layer raw materials are sintered at 1350-1400℃ for 30 minutes, followed by water quenching. S3. The transition layer material is ball-milled, and the particle size of the transition layer material after ball milling is ≤200 mesh; S4. The transition layer material is sprayed onto the surface of the negative electrode material and the ceramic electrolyte using wet cold gas dynamic spraying or powder electrostatic spraying methods. The spraying thickness of the transition layer material is 5-20μm. S5. After the transition layer material to be sprayed is dried, the negative electrode material and the ceramic electrolyte are bonded together, and then high-temperature sintering is carried out. The transition layer material after spraying and bonding is sintered at a high temperature of 500-550℃ for 10-15 minutes to form a transition coating.

[0017] In practical applications, due to the extremely high reactivity of metallic Li, pure Li metal cannot be used directly as the negative electrode. Generally, Li alloys or modified Li metals are used as the negative electrode material; therefore, the negative electrode material is an AlLi alloy. The ceramic electrolyte is Li7La3Zr2O. 12 .

[0018] Si / SiO / SiO2 and amorphous silicon anode materials have large capacities, approximately four times that of traditional graphite anodes. This invention utilizes a transition layer material (a mixture of SiO2 and alkali metal oxides) in AlLi alloys and Li7La3Zr2O 12 The surfaces are coated, and then the two are bonded and sintered together to form the negative electrode material (AlLi alloy), the transition layer material, and the ceramic electrolyte (Li7La3Zr2O). 12 They became one.

[0019] In this invention, the raw material for the transition coating is SiO2 and (one, two, or all three of Li2O, Na2O, and K2O are present; for ease of description, they are collectively referred to as R2O below). SiO2 is mixed with alkali metal oxides and then subjected to high temperature and water quenching to form an initial powder with an amorphous glass structure. SiO2 is the main component of the amorphous network skeleton, playing a role in forming the Si-O network skeleton and providing support for the entire transition coating structure. Li+ / Na+ / K+ alkali metal ions break the network skeleton, promoting the formation of non-bridged oxygen bonds and atomic vacancies in the Si-O network, thus providing a suitable substrate for the negative electrode material AlLi alloy and the ceramic electrolyte material (Li7La3Zr2O). 12 During the sintering process, the relevant atoms in the intermediate layer diffuse into the vacancies, thus forming a structure in which "you are in me and I am in you".

[0020] This amorphous glass material, composed of alkali metal cations such as Li+, K+, and Na+ as fillers, exhibits short-range order and long-range disorder. The voids and non-bridged oxygen bonds generated by its amorphous structure provide channels for the transport of Li+ ions. During battery charging and discharging, Li+ in the coating and Li+ in the negative electrode material can migrate rapidly using the channels formed in the coating. Furthermore, the amorphous network structure also has the ability to store lithium ions, thereby expanding the battery capacity.

[0021] The Li and Al elements in the negative electrode material, and the Li, Zr, and O elements in the ceramic electrolyte material, can participate in the formation reaction of the transition coating network structure during sintering. This promotes the interfacial bonding of the three components between the two interfaces. Specifically, the above process blurs the two solid-phase interfaces, forming a structurally gradual and strongly bonded whole at the interface, thereby reducing interfacial impedance and improving interfacial strength and electrochemical stability, achieving a metallurgical bonding effect. In addition, the above interfacial bonding method effectively disperses the current, avoiding lithium dendrite growth caused by excessive local current density. The interfacial bonding reaction process is described in [reference needed]. Figure 1 As shown.

[0022] It should be added that the preferred ratio of R2O to SiO2 in the transition layer is about 80% and about 20%. The R2O content is related to the subsequent sintering temperature. Specifically, the higher the R2O content, the lower the sintering temperature, and vice versa. However, it is worth noting that the sintering temperature should be kept below the solution temperature of the AlLi alloy, and the composition can be adjusted according to different anode metal materials.

[0023] Regarding the ratio of Li2O, Na2O, and K2O, Li2O has strong activity and is effective in breaking down the Si-O network. Too much Li2O will result in a loose and unstable Si-O network framework, while too little Li2O will hinder the passage of Li+. In this technical solution, the preferred ratio of Li2O, Na2O, and K2O is 1:1:1, but it can be configured according to actual needs.

[0024] Example 2 like Figure 3 As shown in the figure, this embodiment proposes a method to enhance the bonding between the electrolyte and electrode interface of a solid-state battery. Compared with Embodiment 1, in this embodiment, AlLi alloy nanopowder is added to the transition coating to form a gradient transition coating. In this gradient transition coating, the content of AlLi alloy nanopowder gradually decreases from the side closer to the negative electrode material to the other side.

[0025] In this embodiment, furthermore, to improve the Li+ transport capacity of the transition coating, the transition coating can be gradient-designed to form a gradient transition coating. In this embodiment, taking a transition coating with 5 gradient layers and a coating thickness of 20 μm as an example, AlLi alloy nanopowder is used as the raw material. The transition coating is divided into layers: 0-4 μm (layer 1), 4-8 μm (layer 2), 8-12 μm (layer 3), 12-16 μm (layer 4), and 16-20 μm (layer 5). Layer 1 is closer to the AlLi alloy side. The ratio of nanopowder to transition layer raw material is 4:1 (80% AlLi alloy nanopowder and 20% transition layer raw material). The preparation method is as follows: the mixed raw materials are ball-milled and then wet-sprayed or electrostatically sprayed. After the first spraying, drying is performed. The second layer has an AlLi alloy nanopowder to transition layer raw material ratio of 3:2, and so on until five layers are completed. Then, the dried negative electrode material and ceramic electrolyte are bonded together using a similar method, followed by high-temperature sintering to form a gradient transition coating. See details [link to details]. Figure 3 As shown.

[0026] Example 3 like Figure 4 As shown in the figure, this embodiment proposes a method to enhance the bonding between the electrolyte and electrode interface of a solid-state battery. Compared with Embodiment 1, in this embodiment, ceramic electrolyte powder is added to the transition coating to form a gradient transition coating. In this gradient transition coating, the content of ceramic electrolyte powder gradually decreases from the side closer to the ceramic electrolyte to the other side.

[0027] In this embodiment, ceramic electrolyte powder is used as the raw material. The transition coating is divided into 5 layers according to the layering method in Example 2. The first layer is closer to the ceramic electrolyte side. The content ratio of ceramic electrolyte powder in the first layer to the raw material of the transition layer is 4:1. The content ratio of ceramic electrolyte powder and transition layer raw material in the second, third, fourth, and fifth layers is the same as in Example 2. For details, please refer to [link / reference]. Figure 4 As shown, its preparation method is the same as that in Example 2.

[0028] Example 4 like Figure 5 As shown in the figure, this embodiment proposes a method to enhance the bonding between the electrolyte and electrode interface of a solid-state battery. Compared with Embodiment 1, in this embodiment, AlLi alloy nanopowder and ceramic electrolyte powder are added to the transition coating to form a gradient transition coating. In this gradient transition coating, the content of AlLi alloy nanopowder gradually decreases from the side closer to the negative electrode material to the other side, and the content of ceramic electrolyte powder gradually decreases from the side closer to the ceramic electrolyte to the other side.

[0029] In this embodiment, the difference from Embodiments 2 and 3 is that AlLi alloy nanopowder and ceramic electrolyte powder are added simultaneously to the transition coating. The content of AlLi alloy nanopowder and ceramic electrolyte powder varies in different layers, exhibiting a gradient change. Specifically, the transition coating is divided into 5 layers according to the layering method of Embodiment 2. The first layer is closer to the AlLi alloy side. In the first layer, the proportions of transition layer raw material, AlLi alloy nanopowder, and ceramic electrolyte powder are 40%, 50%, and 10%, respectively. In the second layer, the proportions are 40%, 40%, and 20%, respectively. In the third layer, the proportions are 40%, 30%, and 30%, respectively, and so on. The content of transition layer raw material is kept constant in each layer (fine adjustments can be made according to actual needs). The content of AlLi alloy nanopowder and ceramic electrolyte powder is designed according to a gradient distribution, as detailed in the following reference. Figure 5 As shown, its preparation method is the same as that in Example 2.

[0030] It should be added that the setting of the double-sided gradient not only matches the coefficient of thermal expansion well, but also effectively promotes the cross-interface transport of lithium ions; the multi-layer gradient transition layer design proposed in this invention forms a smooth transition zone between the electrode and the electrolyte, and this design can effectively avoid stress concentration on a single interface, and also solve the problem of interface peeling caused by volume expansion effect.

[0031] It should be added that the proportions of the transition layer raw materials, AlLi alloy nanopowder, and ceramic electrolyte powder are not limited to the above proportions. Technicians can make adjustments according to actual needs, but the adjustments should meet the material gradient distribution design.

[0032] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A method for enhancing the bonding between the electrolyte and electrode interface in a solid-state battery, characterized in that, Includes the following steps: S1. SiO2 is mixed with alkali metal oxides to form a transition layer material, wherein the alkali metal oxides include one or more of Li2O, Na2O and K2O; S2. The transition layer raw materials are uniformly mixed and then sintered at high temperature, followed by water quenching. S3. The transition layer material is ball-milled. S4. The transition layer material is sprayed onto the surface of the negative electrode material and the ceramic electrolyte using wet cold gas dynamic spraying or powder electrostatic spraying. S5. After the raw material of the transition layer to be sprayed is dried, the negative electrode material and the ceramic electrolyte are bonded together, and then sintered at high temperature to form the transition coating.

2. The method for enhancing the bonding between the electrolyte and electrode interface in a solid-state battery according to claim 1, characterized in that, The negative electrode material is an AlLi alloy, and the ceramic electrolyte is Li7La3Zr2O. 12 .

3. The method for enhancing the bonding between the electrolyte and electrode interface in a solid-state battery according to claim 1, characterized in that, In the formulation of the transition layer raw materials, the SiO2 content is 60%-90% and the alkali metal oxide content is 10%-40%.

4. The method for enhancing the bonding between the electrolyte and electrode interface in a solid-state battery according to claim 1, characterized in that, After mixing, the transition layer raw materials are sintered at a high temperature of 1350-1400℃ for 30 minutes; after spraying and bonding, the transition layer raw materials are sintered at a high temperature of 500-550℃ for 10-15 minutes.

5. The method for enhancing the bonding between the electrolyte and electrode interface in a solid-state battery according to claim 1, characterized in that, The thickness of the transition layer material is 5-20μm.

6. The method for enhancing the bonding between the electrolyte and electrode interface in a solid-state battery according to claim 1, characterized in that, The particle size of the transition layer material after ball milling is ≤200 mesh.

7. The method for enhancing the bonding between the electrolyte and electrode interface in a solid-state battery according to claim 1, characterized in that, AlLi alloy nanopowder is added to the transition coating to form a gradient transition coating in which the content of AlLi alloy nanopowder gradually decreases from the side closer to the negative electrode material to the other side.

8. The method for enhancing the bonding between the electrolyte and electrode interface in a solid-state battery according to claim 1, characterized in that, A gradient transition coating is formed by adding ceramic electrolyte powder to the transition coating, in which the content of ceramic electrolyte powder gradually decreases from the side closer to the ceramic electrolyte to the other side.

9. The method for enhancing the bonding between the electrolyte and electrode interface in a solid-state battery according to claim 1, characterized in that, AlLi alloy nanopowder and ceramic electrolyte powder are added to the transition coating to form a gradient transition coating. In this gradient transition coating, the content of AlLi alloy nanopowder gradually decreases from the side closer to the negative electrode material to the other side, and the content of ceramic electrolyte powder gradually decreases from the side closer to the ceramic electrolyte to the other side.

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