Three-dimensional integrated solid-state thin film lithium ion battery and method of manufacturing the same

Abstract

The application discloses a three-dimensional integrated solid-state thin film lithium ion battery and a preparation method thereof. Solid-state thin film lithium ion battery structures arranged on two sides of a substrate are connected with positive metal Pads and negative metal Pads on the same side respectively, and the thickness of the metal Pads is greater than the thickness of the solid-state thin film lithium ion battery structures. The positive metal Pads and the negative metal Pads on the upper and lower surfaces of the substrate are connected through through holes. The positive and reverse battery structures, materials and processes of the battery unit are completely the same, the stress generated in the charging and discharging process of the positive and reverse batteries is equal in size and opposite in direction, stress compensation is realized, and the reliability of the battery unit and the three-dimensional integrated battery is improved. In addition, the preparation of the conductive through holes is completed before the preparation of the battery unit and the integration of the battery, thereby avoiding the problems of punching and filling conductive materials in the prior art, and effectively improving the performance of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to a solid-state lithium ion battery, in particular to a three-dimensionally integrated solid-state thin-film lithium ion battery and a preparation method thereof. BACKGROUND

[0002] Lithium ion batteries have the advantages of high energy density, good cycle life, low self-discharge rate, etc., and are widely used in consumer electronics, industrial control, military equipment, aerospace, etc. The electrolyte of the current lithium ion battery is usually in a liquid or gel state (semi-solid type), which has a narrow working temperature range and poor safety, and has safety problems such as liquid leakage, flammability and explosion. In addition, it is difficult to reduce the volume of such batteries, so it is difficult to use in the field of Internet of Things, micro air vehicles, implantable medical devices, etc. which have strict restrictions on battery safety and volume. In contrast, the electrolyte of the solid-state thin-film lithium ion battery is in a solid thin-film state, has a wide working temperature range and a high safety factor, and this type of battery can also be processed and prepared using semiconductor technology, so it also has the advantages of easy miniaturization and easy integration. It should be pointed out that the active materials such as positive and negative electrodes of this type of battery are also in a thin film state, so the active material content of this type of battery is relatively low, which leads to a relatively low energy density of the battery. Increasing the thickness of the active material thin film can help improve the energy density of the battery, but it will also worsen the power density and cycle life of the battery. Therefore, there is a contradiction between the energy density and the power density, cycle life, etc. of the existing solid-state thin-film lithium ion battery.

[0003] By effectively integrating the battery cells in a three-dimensional manner, it is expected to solve the above contradictions of the solid-state thin-film lithium ion battery and achieve comprehensive improvement of the key performance. The existing three-dimensionally integrated solid-state thin-film lithium ion battery is usually prepared in the following way: the battery cells prepared in advance are integrated together by means of adhesives, etc., and then the electrical connection and three-dimensional integration between the battery cells are realized by punching and filling conductive materials. The existing technology has the following problems: (1) the energy density of the existing battery cells is low, which limits the ability of the three-dimensionally integrated battery to improve the energy density; (2) the active materials (including positive and negative electrodes and electrolyte) of the battery are sensitive and fragile, and subsequent operations such as punching and filling conductive materials are easy to cause damage and destruction to the battery, which can easily cause reliability problems of the battery; (3) the adjacent battery cells in the existing three-dimensionally integrated battery are in close contact, which makes it difficult to release the stress generated by the volume expansion / contraction of the battery cells during charging and discharging, and the stress generated thereby can easily cause reliability problems such as damage to the battery, which further aggravates and worsens the reliability of the battery cells and the three-dimensionally integrated battery.

[0004] Reducing the thickness of the active material in the battery cell can reduce the stress generated by volume expansion / contraction during charging and discharging, thereby improving the reliability of the battery cell and the three-dimensionally integrated battery. However, this also reduces the energy density of the battery cell and the three-dimensionally integrated battery, and therefore, the existing three-dimensionally integrated battery has a contradiction between energy density and reliability. For the above reasons, the performance and effect of the existing three-dimensionally integrated battery are far from expected. SUMMARY

[0005] The present application aims to solve the above problems existing in the prior art three-dimensionally integrated battery and improve the overall performance of the battery.

[0006] Technical solution: A three-dimensionally integrated solid-state thin-film lithium ion battery, characterized in that it comprises: two or more battery cells, and the positive and negative electrodes of each battery cell are connected together by bonding.

[0007] The battery cell comprises a substrate, and the upper and lower surfaces of the substrate are respectively provided with positive and negative metal Pads and a solid-state thin-film lithium ion battery structure, and the battery cell as a whole is mirror-symmetric about the plane where the substrate is located.

[0008] The positive and negative current collector layers of the solid-state thin-film lithium ion battery structure are respectively connected to the positive and negative metal Pads on the same surface; the solid-state thin-film lithium ion battery structure is located between the oppositely arranged positive and negative metal Pads, the thicknesses of the positive and negative metal Pads are consistent and greater than the thickness of the solid-state thin-film lithium ion battery structure; and the positive and negative metal Pads on the upper and lower surfaces of the substrate are respectively connected by through-hole metal.

[0009] Further, the solid-state thin-film lithium ion battery structure comprises, from bottom to top, a positive current collector layer, a positive electrode layer, a solid-state electrolyte layer, a negative electrode layer, a negative current collector layer, and a passivation layer.

[0010] Further, the thicknesses of the positive and negative metal Pads are 1-8 μm.

[0011] The preparation method of the three-dimensionally integrated solid-state thin-film lithium ion battery comprises:

[0012] First, etch the through-hole metal on the substrate;

[0013] Then, generate the positive and negative metal Pads on the upper and lower surfaces of the substrate by magnetron sputtering and photolithography, respectively;

[0014] Then, one of the solid-state thin film lithium ion battery structures is prepared on one side of the substrate, and another of the solid-state thin film lithium ion battery structures is prepared on the other side of the substrate by the same process, to complete the preparation of the single battery cell

[0015] Finally, the battery cells are aligned by a clamp, and the three-dimensional integration of the battery cells is realized by the bonding of the conductive agent.

[0016] Beneficial effects: 1. The solid-state thin film lithium ion battery of the present application is provided with metal pads at both ends, and the thickness of the metal pads is greater than the sum of the thicknesses of the film layers of the battery, which results in a gap between two adjacent battery cells in the three-dimensional integrated battery, which can ensure that mechanical pressure is not applied to the battery cells when the battery cells are three-dimensionally integrated, thereby improving the reliability of the battery cells and the three-dimensionally integrated battery, and also helps to release the stress generated by the volume change during the charging and discharging process of the battery cells, thereby improving the reliability of the battery cells and the three-dimensionally integrated battery.

[0017] 2. The positive and negative surfaces of the solid-state thin film lithium ion battery cell of the present application are both prepared with batteries, and the energy density of the battery cell of the present application is doubled compared with the battery cell of the prior art, which helps to greatly increase the energy density of the three-dimensionally integrated battery.

[0018] In addition, the structure, material and process of the positive and negative batteries of the battery cell of the present application are completely the same, which not only simplifies the preparation cost, but also improves the uniformity of the process and the consistency and matching of the battery performance. More importantly, the batteries on the positive and negative surfaces of the battery cell are connected in parallel through the pre-set conductive vias, and the positive and negative batteries are charged or discharged synchronously and cause the positive and negative batteries to expand or shrink synchronously, and the stress generated thereby is equal in size and opposite in direction, thus effectively realizing stress compensation, thereby greatly improving the reliability of the battery cell and the three-dimensionally integrated battery. Therefore, the battery cell of the present application can increase the energy density by increasing the thickness of the active material, and this will not cause reliability problems. In contrast, for the prior art, reducing the thickness of the active material in the battery cell can reduce the stress generated by the volume expansion during the charging and discharging process, thereby improving the reliability of the battery cell and the three-dimensionally integrated battery; however, this also reduces the energy density of the battery cell and the three-dimensionally integrated battery, and therefore, the existing three-dimensionally integrated battery has a contradiction between energy density and reliability. This contradiction is well solved in the present application.

[0019] 3. The pre-designed conductive vias in this invention not only enable electrical connection between the front and back sides of the battery cell, but also facilitate connection between battery cells. Therefore, the battery of this invention has the advantage of a compact structure. Furthermore, this invention completes the fabrication of the conductive vias before battery cell fabrication and battery integration. This avoids the damage and destruction to the battery caused by drilling and filling conductive materials, as is present in existing technologies, effectively improving battery performance.

[0020] 4. The three-dimensional integrated solid-state thin-film lithium-ion battery of the present invention is fully compatible with semiconductor technology and has the advantages of high precision, easy miniaturization and easy integration. Attached Figure Description

[0021] Figures 1-11 This is a schematic diagram of the fabrication process of the three-dimensional integrated solid-state thin-film lithium-ion battery of the present invention;

[0022] The figure shows: substrate 1, positive electrode through-hole metal 2, negative electrode through-hole metal 3, positive electrode metal Pad 4 on the upper surface of the substrate, negative electrode metal Pad 5 on the upper surface of the substrate, positive electrode metal Pad 6 on the lower surface of the substrate, negative electrode metal Pad 7 on the lower surface of the substrate, positive electrode current collector layer 8, positive electrode layer 9, solid electrolyte layer 10, negative electrode layer 11, negative electrode current collector layer 12, passivation layer 13, first battery structure 14, and second battery structure 15. Detailed Implementation

[0023] The invention will now be further explained with reference to the accompanying drawings.

[0024] like Figure 11 As shown, a three-dimensional integrated solid-state thin-film lithium-ion battery includes two or more battery cells, with the positive and negative electrodes of each battery cell connected together by bonding.

[0025] like Figure 9 , Figure 10 As shown, each battery cell includes two solid-state thin-film lithium-ion battery structures disposed on the upper and lower surfaces of the substrate 1, referred to as the first battery structure 14 and the second battery structure 15, respectively. These two battery structures are identical in material, structure, and manufacturing process, and are mirror-symmetrical about the plane of the substrate 1. The first battery structure 14 includes: a substrate 1, a positive electrode through-hole metal 2, a negative electrode through-hole metal 3, a positive electrode metal Pad 4 on the upper surface of the substrate, a negative electrode metal Pad 5 on the upper surface of the substrate, a positive electrode current collector layer 8, a positive electrode layer 9, a solid electrolyte layer 10, a negative electrode layer 11, a negative electrode current collector layer 12, and a passivation layer 13. The second battery structure 15 includes: a substrate 1, a positive electrode through-hole metal 2, a negative electrode through-hole metal 3, a positive electrode metal Pad 6 on the lower surface of the substrate, a negative electrode metal Pad 7 on the lower surface of the substrate, a positive electrode current collector layer 8, a positive electrode layer 9, a solid electrolyte layer 10, a negative electrode layer 11, a negative electrode current collector layer 12, and a passivation layer 13.

[0026] As shown in Figure 1 , Figure 2 , the substrate 1 is ceramic, glass, or silicon wafer with surface oxidized and insulated, in the shape of square or rectangle, with the upper and lower surfaces of one pair of opposite sides each having an upper surface positive metal Pad4, an upper surface negative metal Pad5, a lower surface positive metal Pad6, and a lower surface negative metal Pad7 as the electrode leads of the positive and negative electrodes of the battery, the upper surface positive metal Pad4 and the lower surface positive metal Pad6 being electrically connected through the positive via metal 2, and the upper surface negative metal Pad5 and the lower surface negative metal Pad7 being electrically connected through the negative via metal 3. The materials of the metal Pads 4, 5, 6, and 7 are alloys made of at least one or more of WTi, Cu, Ni, Au, and Pt, with a thickness of 1 μm to 8 μm, and the thickness is greater than the sum of the thicknesses of the film layers of the battery, i.e. greater than the thickness of the structure of the solid-state thin film lithium ion battery.

[0027] The material of the positive current collector layer 8 is an alloy made of at least one or more of Pt, Al, and Ti, with a thickness of 50 nm to 500 nm. As shown in Figure 3 , the main part of the positive current collector layer 8 is in the shape of square or rectangle, laid in the middle of the substrate 1, with one side extending to contact the upper surface positive metal Pad4 or the lower surface positive metal Pad6 of the plane, to realize the positive lead-out of the battery.

[0028] The material of the positive layer 9 is at least one of LiCoO2, LiMnO2, LiFePO4, and V2O5, with a thickness of 100 nm to 10 μm. As shown in Figure 4 , the positive layer 9 is covered on the positive current collector layer 8, with the shape consistent with the main part of the positive current collector layer 8.

[0029] The material of the solid-state electrolyte layer 10 is at least one of Li3PO4, LiPON, and LiSiPON, with a thickness of 100 nm to 5000 nm. As shown in Figure 5 , the solid-state electrolyte layer 10 is covered on the positive layer 9, in the shape of square or rectangle, with the area greater than that of the positive layer 9, and the edge is at least 5 μm away from the edge of the positive layer 9, to separate the positive and negative layers and prevent short circuit, thus improving the reliability of the battery.

[0030] The material of the negative layer 11 is at least one of InGaZnO, graphite, silicon, and lithium, with the thickness determined according to the capacity matching rules of the positive and negative electrodes. As shown in Figure 6 , the negative layer 11 is covered on the solid-state electrolyte layer 10, with the shape and position consistent with those of the positive layer, to increase the charging and discharging efficiency of the battery and reduce the process cost.

[0031] The material of the negative current collector layer 12 is at least one of metal Pt, Al, Ti or an alloy of several of them, with a thickness of 50 nm-500 nm. As shown in Figure 7 , the negative current collector layer 12 has the same shape and size as the positive current collector layer 8, except that it extends on one side to contact the upper surface negative metal Pad 5 or the lower surface negative metal Pad 7 of the surface on which it is located, to realize the negative lead-out of the battery.

[0032] The material of the passivation layer 13 is at least one of SiO2, Si3N4, Al2O3, Parylene, with a thickness of 500 nm-10 μm. As shown in Figure 8 , Figure 9 , the passivation layer completely covers the areas of the positive current collector layer 8, the positive electrode layer 9, the solid-state electrolyte layer 10, the negative electrode layer 11, and the negative current collector layer 12, to prevent atmospheric penetration and contact with the positive electrode, electrolyte, and negative electrode of the battery, and to prevent deterioration of the materials and performance of the battery.

[0033] A method for manufacturing a three-dimensionally integrated solid-state thin-film lithium ion battery, comprising the following steps:

[0034] Step 1: Select 99% alumina ceramic as the substrate 1, and use laser etching to form a through hole on the substrate 1.

[0035] Step 2: Generate the positive through-hole metal 2, the negative through-hole metal 3, the positive metal Pad 4, the negative metal Pad 5, the positive metal Pad 6, and the negative metal Pad 7 on the upper and lower surfaces of a pair of opposite edges of the substrate and the sidewalls of the through hole by magnetron sputtering and photolithography, with the metal layer structure being WTi, Cu, Ni, and Au from bottom to top, and the total thickness being 6 μm, as shown in Figure 1 , Figure 2 .

[0036] Step 3: Prepare 100 nm thick Pt as the positive current collector layer 8 by sputtering process and photolithography, as shown in Figure 3 .

[0037] Step 4: Prepare 180 nm thick V2O5 as the positive electrode layer 9 on the positive current collector layer 8 by sputtering process and photolithography, as shown in Figure 4 .

[0038] Step 5: Prepare 1.2 μm thick LiPON as the solid-state electrolyte layer 10 on the positive electrode layer 9 by sputtering process and photolithography, as shown in Figure 5 .

[0039] Step 6: Prepare 80 nm thick InGaZnO as the negative electrode layer 11 on the solid-state electrolyte layer 10 by sputtering process and photolithography, as shown in Figure 6 .

[0040] Step 7: Pt is prepared as negative current collector layer 12 on negative electrode layer 11 by sputtering process and photolithography with thickness of 100 nm, as shown in Figure 7 .

[0041] Step 8: SiN is prepared as passivation layer 13 on negative current collector layer 12 by sputtering process and photolithography with thickness of 1 μm, as shown in Figure 8 , Figure 9 .

[0042] Step 9: the process flow of Step 3-Step 8 is repeated to prepare another battery on the back of the substrate, and the preparation of solid-state thin film lithium ion battery cell is completed, as shown in Figure 10 .

[0043] Step 10: the battery cells prepared by both sides of the battery are aligned by using a clamp, and the three-dimensional integration of the battery cells is realized by bonding through the conductive agent. The battery integration containing two battery cells is shown in Figure 11 . The thickness of the positive and negative metal pads is consistent, which ensures that the battery units of the three-dimensional integrated battery are placed horizontally and the structure is stable. Moreover, the thickness of the positive and negative metal pads is greater than the thickness of the solid-state thin film lithium ion battery, which results in a gap between the two adjacent battery units in the three-dimensional integrated battery. This can not only ensure that mechanical pressure is not applied to the battery units when the battery units are three-dimensionally integrated, thereby improving the reliability of the battery units and the three-dimensionally integrated battery, but also help to release the stress generated by the volume change of the battery units during charging and discharging, thereby improving the reliability of the battery units and the three-dimensionally integrated battery.

[0044] The above only describes the preferred embodiments of the present application. It should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A three-dimensional integrated solid-state thin-film lithium-ion battery, characterized in that, include: Two or more battery cells; The battery cell includes a substrate, and the upper and lower surfaces of the substrate are respectively provided with a positive electrode metal pad, a negative electrode metal pad, and a solid-state thin-film lithium-ion battery structure. The battery cell as a whole is mirror-symmetrical about the plane of the substrate. The positive and negative electrodes of each battery cell are connected together by bonding. The positive and negative current collector layers of the solid-state thin-film lithium-ion battery structure are respectively connected to the positive and negative metal pads on the same side; the solid-state thin-film lithium-ion battery structure is located between the positive and negative metal pads arranged opposite each other, and the thickness of the positive and negative metal pads is the same and greater than the thickness of the solid-state thin-film lithium-ion battery structure; the positive and negative metal pads on the upper and lower surfaces of the substrate are connected by through-hole metal; a gap is left between two adjacent battery cells in the three-dimensional integrated battery.

2. The three-dimensional integrated solid-state thin-film lithium-ion battery according to claim 1, characterized in that, The solid-state thin-film lithium-ion battery structure includes, from the substrate outwards, a positive electrode current collector layer, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, a negative electrode current collector layer, and a passivation layer.

3. The three-dimensional integrated solid-state thin-film lithium-ion battery according to claim 1, characterized in that, The thickness of the positive electrode metal pad and the negative electrode metal pad is between 1 μm and 8 μm.

4. The method for preparing a three-dimensional integrated solid-state thin-film lithium-ion battery according to any one of claims 1-3, characterized in that, include: First, through holes are etched into the substrate; Then, the through-hole metal, the positive electrode metal Pad, and the negative electrode metal Pad are generated on the upper and lower surfaces of the substrate and the sidewalls of the through hole by magnetron sputtering and photolithography, respectively. Next, a solid-state thin-film lithium-ion battery structure is fabricated on one side of the substrate, and then another solid-state thin-film lithium-ion battery structure is symmetrically fabricated on the other side of the substrate using the same process, thus completing the fabrication of a single battery cell; Finally, the battery cells are aligned using a fixture and bonded using a conductive agent to achieve three-dimensional integration of the battery cells.

Images