Composite negative electrode structure

Abstract

A composite anode structure includes a current collector, a porous layer, a plurality of lithiophilic structures, and a solid electrolyte layer. The porous layer is located on the surface of the current collector and has a plurality of pores. The lithiophilic structures are located on the surface of the current collector and are housed within some of the pores. The solid electrolyte layer is located on the porous layer. This composite anode structure can improve the problems of volume expansion and capacity loss during the first charge / discharge cycle in solid-state batteries. It can also reduce the possibility of lithium metal deposition on the electrode surface and reduce safety issues caused by lithium dendrite puncture.

Description

Technical Field

[0001] The present invention relates to a composite negative electrode structure. Background Technology

[0002] With the rapid development of technology, various portable batteries have emerged, and people's demands for high performance and lightweight portable batteries are increasing. As these demands grow stronger, lithium-ion batteries have gained significant attention and widespread use due to their high energy density and rapid charging capabilities.

[0003] However, during charging, lithium metal anodes are prone to lithium ion reduction and disorderly deposition on the electrode surface, which can cause the interlayer structure of the battery to expand, resulting in battery volume expansion and even lithium dendrite puncture problems. Therefore, how to modify the behavior of lithium metal deposition to improve the above-mentioned shortcomings is a key focus of research in this field. Summary of the Invention

[0004] According to some embodiments of the present invention, the composite negative electrode structure includes a current collector layer, a porous layer, a plurality of lithiophilic structures, and a solid electrolyte layer. The porous layer is located on the surface of the current collector layer and has a plurality of pores. The lithiophilic structures are located on the surface of the current collector layer and are housed within some of the pores. The solid electrolyte layer is located on the porous layer.

[0005] In some embodiments of the present invention, the solid electrolyte layer is partially embedded in the porous layer.

[0006] In some embodiments of the present invention, the porous layer has a first portion close to the current collector and a second portion far from the current collector, and the density of the lithiophilic structure in the first portion is greater than the density of the lithiophilic structure in the second portion.

[0007] In some embodiments of the present invention, the porous layer further comprises a third portion, wherein the second portion is located between the first portion and the third portion, and the density of the lithiophilic structure in the third portion is zero.

[0008] In some embodiments of the present invention, the average particle size of the lithiophilic structure is between 0.1 μm and 1 μm.

[0009] In some embodiments of the present invention, the average pore diameter is between 0.1 μm and 10 μm.

[0010] In some embodiments of the present invention, the porous layer comprises a plurality of carbon nanomaterials stacked in an alternating manner, with pores located between adjacent carbon nanomaterials, wherein the carbon nanomaterials include carbon nanowires, carbon nanotubes, carbon nanofilaments, carbon nanofibers, or combinations thereof.

[0011] In some embodiments of the present invention, the total thickness of the porous layer is between 1 μm and 100 μm, and the total thickness of the lithiophilic structure is between 0.1 μm and 10 μm.

[0012] In some embodiments of the present invention, the materials of the lithiophilic structure may include silver, gold, platinum, aluminum, zinc, magnesium, silicon, tin, nickel, oxides of any of the above metals, combinations of any of the above metals and oxides of metals, or organic framework materials of any of the above metals.

[0013] In some embodiments of the present invention, the solid electrolyte layer may include lithium salts, polymers, and solid electrolytes. Polymers include polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyethylene oxide, or combinations thereof. Solid electrolytes include lithium aluminum titanium phosphate, lithium lanthanum tantalum oxide, lithium lanthanum zirconium oxide, or combinations thereof.

[0014] According to the above embodiments of the present invention, the composite anode structure of the present invention utilizes the synergistic effect of a porous layer and a lithiophilic structure. The porous layer can alleviate the problem of volume expansion of the anode during charging, while the lithiophilic structure allows lithium ions in the solid-state battery to be reduced to lithium metal at the lithiophilic structure. The formed lithium metal can then expand outward with the lithiophilic structure as a nucleation site, and its growth is confined within the pores of the porous layer, thus achieving orderly deposition. In this way, the deposition mode of lithium metal in the solid-state battery can be changed, promoting orderly deposition of lithium metal and avoiding the formation of a large amount of solid electrolyte interface (SEI) due to the high specific surface area of ​​the porous layer, thereby reducing the irreversible capacity during the first charge and discharge. The composite anode structure of the present invention can therefore improve the problems of volume expansion and capacity loss caused by the first charge and discharge of solid-state batteries. In addition, the composite anode structure of the present invention can also reduce the possibility of lithium metal deposition on the electrode surface, reducing safety issues caused by lithium dendrite puncture. Attached Figure Description

[0015] To make the above and other objects, features, advantages and embodiments of the present invention more apparent and understandable, the accompanying drawings are described below:

[0016] Figure 1 A cross-sectional schematic diagram of a composite negative electrode structure according to some embodiments of the present invention is shown;

[0017] Figure 2 A cross-sectional schematic diagram illustrating a solid-state battery according to some embodiments of the present invention; and

[0018] Figure 3 Plot the voltage-time relationship for different stacked structures. Detailed Implementation

[0019] The following drawings disclose several embodiments of the present invention. For clarity, many practical details will be described in the following description. However, it should be understood that these practical details are not intended to limit the invention. That is, in some embodiments of the invention, these practical details are not essential and therefore are not intended to limit the invention. Furthermore, for the sake of simplicity, some conventional structures and elements are shown in the drawings in a simplified schematic manner. In addition, for the reader's convenience, the dimensions of the elements in the drawings are not drawn to scale.

[0020] It should be understood that relative terms such as “down” or “bottom” and “up” or “top” may be used herein to describe the relationship between one element and another, as illustrated in the figures. It should be understood that relative terms are intended to include different orientations of the device beyond those shown in the figures. For example, if a device in a figure is flipped, an element described as being “down” to other elements will be oriented “up” to other elements. Thus, the exemplary term “down” can include both “down” and “up” orientations, depending on the specific orientation of the figure. Similarly, if a device in a figure is flipped, an element described as being “down” or “below” to other elements will be oriented “above” to other elements. Thus, the exemplary term “down” or “below” can include both “up” and “down” orientations.

[0021] This invention provides a composite anode structure and a solid-state battery including the composite electrode structure. By incorporating the lithiophilic structure and porous layer in the composite anode structure, the deposition pattern of lithium metal in the solid-state battery can be effectively altered, promoting orderly lithium metal deposition. This not only alleviates the volume expansion problem of solid-state batteries but also suppresses the excessive formation of solid electrolyte interfaces, reducing capacity loss during the first charge-discharge cycle. The composite anode structure of this invention also reduces the likelihood of lithium metal deposition on the electrode surface, minimizing lithium dendrite formation.

[0022] Please see Figure 1The diagram illustrates a cross-sectional schematic of a composite negative electrode structure 100 according to some embodiments of the present invention. The composite negative electrode structure 100 includes a current collector layer 110, a porous layer 120, a lithiophilic structure 124, and a solid electrolyte layer 130. The porous layer 120 is located on the surface 111 of the current collector layer 110, and the surface 111 of the current collector layer 110 has a plurality of lithiophilic structures 124, that is, the lithiophilic structures 124 are located on the surface 111 of the current collector layer 110. The porous layer 120 has a plurality of pores H, and the lithiophilic structures 124 are located in a portion of the pores H.

[0023] In some embodiments, the current collection layer 110 may be copper foil, stainless steel foil, nickel foil, or other suitable metal alloy foil.

[0024] In some embodiments, the porous layer 120 comprises a plurality of carbon nanomaterials (CNMs), which are stacked alternately on the surface 111 of the current collector 110 to form a plurality of pores H, i.e., the pores H are located between adjacent carbon nanomaterials CNMs. In some embodiments, the carbon nanomaterials CNMs include carbon nanowires, carbon nanotubes, carbon nanofilaments, or carbon nanofibers, or combinations thereof. In some embodiments, the carbon nanotubes in the carbon nanomaterials CNMs may be, for example, single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), or combinations thereof. It is worth noting that since carbon-containing materials have a low weight per unit volume (i.e., low density), when the porous layer 120 comprises carbon nanomaterials CNMs, the overall weight of the solid-state battery can be significantly reduced. In some embodiments, the aspect ratio (i.e., length:diameter) of the nanocarbon material CNM can be greater than 20 to provide good mechanical strength and facilitate the stacking of the nanocarbon material CNM to form effective pore spaces, thereby facilitating the containment of the lithiophilic structure 124 within the pores H. It should be understood that, in addition to the nanocarbon material CNM disclosed above, other nanocarbon material CNMs with the same aspect ratio described above are also within the scope of this invention.

[0025] In some embodiments, the average pore size of the pores H can be between 0.1 μm and 10 μm to facilitate the accommodation of the lithiophilic structure 124 and provide sufficient space for the orderly deposition of lithium metal within the pores H, thereby mitigating the volume expansion problem of the solid-state battery during charging. Furthermore, the aforementioned pore size range design also allows the solid electrolyte layer 130 to be more easily embedded into the porous layer 120, thereby increasing the overall structural stability of the composite negative electrode structure 100. In some embodiments, the thickness T1 of the porous layer 120 can be between 1 μm and 100 μm, or between 20 μm and 100 μm, to provide sufficient space for the orderly deposition of lithium metal.

[0026] In some embodiments, the lithiophilic structure 124 may include silver, gold, platinum, aluminum, zinc, magnesium, silicon, tin, nickel, oxides of any of the above metals, combinations of the above metals, or metal organic frameworks (MOFs) of any of the above metals. By disposing the lithiophilic structure 124 on the surface 111 of the current collector 110, and through the selection of the above materials, lithium ions generated by the solid-state battery tend to adhere to the surface of the lithiophilic structure 124 to be reduced to lithium metal, thereby allowing lithium metal to be deposited in an orderly manner around the lithiophilic structure 124. In other words, a lithiophilic structure 124 is equivalent to a nucleation point, allowing lithium metal to grow and expand outward in an orderly manner using this nucleation point as a growth center. In this way, the excessive formation of the solid electrolyte interface (SEI) can be avoided, reducing the irreversible capacity during the first charge and discharge cycle. In addition, it also reduces the deposition of lithium metal on the electrode surface, reduces the occurrence of lithium dendrite puncture, and thus improves the safety of the solid-state battery.

[0027] In some embodiments, the average particle size of the lithiophilic structure 124 can be between 0.1 μm and 1 μm, so that the lithiophilic structure 124 has sufficient specific surface area for lithium metal reduction and deposition, thereby improving cycle efficiency and facilitating the containment of the lithiophilic structure 124 in the pores H. On the other hand, the design of the above-mentioned average particle size range of the lithiophilic structure 124 can improve the dispersibility of the lithiophilic structure 124 in the solution during the process, so as to facilitate the uniform formation of the lithiophilic structure 124 on the surface 111 of the current collector 110. In some embodiments, the total thickness T2 of the lithiophilic structure 124 can be between 0.1 μm and 10 μm, so that the lithiophilic structure 124 is uniformly and appropriately distributed on the current collector 110. In detail, if the total thickness T2 of the lithiophilic structure 124 is too small, it is insufficient to induce lithium metal to be preferentially reduced at the lithiophilic structure; while if the total thickness T2 of the lithiophilic structure 124 is too large, the porous layer 120 can accommodate less lithium metal, causing the solid-state battery to expand in volume, and the lithiophilic structure 124 located in the lower layer (e.g., closer to the current collector 110) may not be effectively utilized, resulting in material waste and an increase in the overall weight of the solid-state battery.

[0028] Through the synergistic interaction between the porous layer 120 and the lithiophilic structure 124, the porous layer 120 can alleviate the problem of battery volume expansion during charging, while the lithiophilic structure 124 allows lithium ions in the solid-state battery to be reduced to form lithium metal at the lithiophilic structure 124. The formed lithium metal can then expand outward with the lithiophilic structure 124 as a nucleation site, and its growth is confined within the pores H of the porous layer 120, allowing for orderly deposition. In other words, both the porous structure 122 and the lithiophilic structure 124 of the porous layer 120 are indispensable. For example, without the lithiophilic structure 124, lithium metal can easily and randomly deposit on the surface 111 of the current collector 110, failing to reliably accommodate the pores H of the porous structure 122. Furthermore, after multiple cycles of the solid-state battery, the lithium metal deposited on the surface 111 of the current collector 110 may even directly support the entire porous structure 122, leading to the problem of solid-state battery volume expansion.

[0029] In some embodiments, the lithiophilic structure 124 has a higher density closer to the current collector 110 and a lower density farther away from the current collector 110. More specifically, the porous layer 120 has a first portion 122a closer to the current collector 110 and a second portion 122b farther away from the current collector 110, and the density of the lithiophilic structure 124 in the first portion 122a is greater than the density of the lithiophilic structure 124 in the second portion 122b. In a further embodiment, the lithiophilic structure 124 may be distributed in the porous layer 120, for example, in a "gradual" manner, that is, the density of the lithiophilic structure 124 may decrease from the first portion 122a to the second portion 122b of the porous layer 120. By utilizing the special design of the density of the aforementioned lithiophilic structure 124, lithium ions can have the opportunity to contact the lower lithiophilic structure 124, thereby improving the reduction efficiency of lithium ions and making better use of the space of the pores H, so that the lithium metal formed after reduction can be orderly contained in the pores H.

[0030] In some embodiments, the porous layer 120 further comprises a third portion 122c, which is further away from the current collector layer 110 than the second portion 122b, wherein the second portion 122b is located between the first portion 122a and the third portion 122c, and the density of the lithiophilic structure 124 in the third portion 122c is zero. In other words, no lithiophilic structure 124 is present in the upper layer (e.g., closer to the solid electrolyte layer 130) of the porous layer 120. Based on the above configuration, the porous layer 120 provides sufficient pore space to allow lithium metal to be orderly accommodated in the pores H, thereby improving the problem of volume expansion of the solid-state battery during charging. It should be understood that in some embodiments, the distribution (e.g., distribution density) of the lithiophilic structure 124 in the porous layer 120 can be determined by energy-dispersive X-ray (EDX) analysis of the porous layer 120.

[0031] In some embodiments, the solid electrolyte layer 130 may include a lithium salt, a polymer, and a solid electrolyte 132 (wherein the lithium salt and polymer are not shown in the figures), and the lithium salt, polymer, and solid electrolyte 132 are uniformly mixed with each other. Specifically, the lithium salt may include, for example, lithium bis(fluorosulfonyl)imide (LiO4NS2F2, abbreviated as LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2, abbreviated as LiTFSI), lithium perchlorate (LiClO4), or combinations thereof; the polymer may include, for example, poly(methyl methacrylate, abbreviated as PMMA), poly(ethylene oxide, abbreviated as PEO), polyvinylidene difluoride (abbreviated as PVDF), polyacrylonitrile (abbreviated as PAN), or combinations thereof; and the solid electrolyte 132 may include, for example, lithium lanthanum zirconium oxide (Li7La3Zr2O). 12 Lithium titanium aluminum phosphate (LLZO) 1.3 Al 0.3 Ti 1.7 (PO4)3, abbreviated as LATP, lithium lanthanum tantalum oxide (La) 0.57 Li 0.29 TiO3 (LLTO for short) or combinations thereof.

[0032] In some embodiments, the solid electrolyte layer 130 covers the porous layer 120. In some embodiments, the solid electrolyte layer 130 may be partially embedded in the porous layer 120. In some embodiments, the solid electrolyte layer 130 may be partially embedded in the porous layer 120 and extend toward the current collector 110 and contact the surface 111 of the current collector 110. In some embodiments, the solid electrolyte layer 130 substantially encapsulates each lithium-philic structure 124 and each nanocarbon nanomaterial (CNM) of the porous layer 120. In this way, the solid electrolyte layer 130 provides complete encapsulation, enabling the composite anode structure 100 to have strong structural strength and stability as a whole. In some embodiments, the average particle size of the solid electrolyte 132 can be between 0.1 μm and 10 μm to minimize the entry of the solid electrolyte 132 into the porous layer 120, allowing the solid electrolyte 132 to cover the porous layer 120 and enabling the pores H of the porous layer 120 to accommodate more lithium metal, thereby improving the utilization rate of pores H. In some embodiments, the average particle size of the solid electrolyte 132 is larger than the average pore size of the pores H. By selecting the average particle size of the solid electrolyte 132, the solid electrolyte 132 can cover the porous layer 120, reducing the problem of lithium dendrite puncture and lowering the risk of short circuits. On the other hand, since the solid electrolyte layer 130 has high ionic conductivity, it helps to improve the overall performance of the solid-state battery, and by integrating lithium salt, polymer, and solid electrolyte 132 into a single layer, the ease of manufacturing process can be greatly improved.

[0033] Please see Figure 2 The diagram illustrates a cross-sectional schematic of a solid-state battery 300 according to some embodiments of the present invention. Specifically, when the composite negative electrode structure 100 is integrated into the solid-state battery 300, one embodiment may be as follows: Figure 2 As shown. In Figure 2In some embodiments, the solid-state battery 300 includes a composite negative electrode structure 100 and a positive electrode 200, with the positive electrode 200 disposed on the side of the solid electrolyte layer 130 of the composite negative electrode structure 100 opposite to the current collector layer 110. In some embodiments, the positive electrode 200 may include a positive electrode material layer 210 and a positive electrode current collector 220. In some embodiments, the solid electrolyte layer 130 and the positive electrode current collector 220 are located on opposite surfaces of the positive electrode material layer 210, such that the positive electrode material layer 210 is sandwiched between the positive electrode current collector 220 and the composite negative electrode structure 100. In some embodiments, the positive electrode material layer 210 may include, for example, nickel cobalt manganese (NCM), nickel cobalt manganese aluminum (NCMA), lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), nickel cobalt aluminum (NCA), lithium iron phosphate (LiFePO4, LFP), lithium manganese iron phosphate (LMFP), or any combination thereof, and the positive electrode current collector 220 may include, for example, aluminum foil.

[0034] It should be understood that the component connections and functions already described will not be repeated. In the following description, the effectiveness of the invention will be further verified through different stacked structures.

[0035] Please also refer to Figure 1 and Figure 3 ,in Figure 3 Plot the voltage-time relationship for different stacked structures. Figure 3 In the stacked structure, layer 1 is a current collector layer 110, made of copper foil; layer 2 consists of a porous layer 120 disposed on the current collector layer 110, wherein the current collector layer 110 is made of copper foil, the porous layer 120 includes carbon nanotubes (CNM), and the thickness T1 of the porous layer 120 is 20 μm to 100 μm; layer 3 consists of a lithiophilic structure 124 disposed on the current collector layer 110, wherein the current collector layer 110 is made of copper foil, the lithiophilic structure 124 is made of copper-containing organic framework material, and the total thickness T2 of the lithiophilic structure 124 is 0.1 μm to 10 μm. Figure 3 As shown, compared to stacked structure 1, stacked structures 2 and 3 have smoother voltage transition points. It can be seen that whether a porous layer 120 is provided on current collector 110 or a lithium-loving structure 124 is provided on current collector 110, it helps lithium metal to grow more slowly and orderly, so that solid-state batteries can have better controllability.

[0036] According to the above embodiments of the present invention, the porous layer can accommodate lithium metal, alleviating the problem of volume expansion during solid-state battery charging. At the same time, by changing the deposition mode of lithium metal in the solid-state battery through the lithiophilic structure, lithium metal is deposited in an orderly manner, avoiding the generation of a large number of solid electrolyte interfaces due to the high specific surface area of ​​the porous layer, reducing the irreversible capacity of the first charge and discharge, improving cycle stability and availability. The negative electrode composite structure of the present invention can also suppress lithium dendrite puncture, effectively improving battery safety.

[0037] Although the present invention has been described above with reference to embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0038] [Symbol Explanation]

[0039] 100: Composite negative electrode structure

[0040] 110: Gastrosphere

[0041] 111: Surface

[0042] 120: Porous layer

[0043] 122a: Part 1

[0044] 122b: Part Two

[0045] 122c: Part Three

[0046] 124: Lithophilic structure

[0047] 130: Solid electrolyte layer

[0048] 132: Solid electrolyte

[0049] 200: Positive electrode

[0050] 210: Positive electrode material layer

[0051] 220: Positive current collector

[0052] 300: Solid-state battery

[0053] H: Hole

[0054] CNM: Nanocarbon Materials

[0055] T1, T2: Thickness.

Claims

1. A composite negative electrode structure, characterized in that, include: Catchment layer; A porous layer is located on the surface of the current collector and has a first portion close to the current collector and a second portion away from the current collector. The porous layer has a plurality of pores, wherein the total thickness of the porous layer is between 1 µm and 100 µm. A plurality of lithiophilic structures are located on the surface of the current collector and housed within portions of the pores, wherein the density of the lithiophilic structures in the first portion is greater than the density of the lithiophilic structures in the second portion, and the total thickness of the lithiophilic structures is between 0.1 µm and 10 µm; and A solid electrolyte layer is located on the porous layer, wherein the solid electrolyte layer is partially embedded in the porous layer.

2. The composite negative electrode structure according to claim 1, wherein the porous layer further comprises a third portion, the second portion being located between the first portion and the third portion, and the density of the lithiophilic structures in the third portion is zero.

3. The composite anode structure according to claim 1, wherein the average particle size of the lithiophilic structures is between 0.1 µm and 1 µm.

4. The composite negative electrode structure according to claim 1, wherein the average pore diameter of the pores is between 0.1 µm and 10 µm.

5. The composite negative electrode structure according to claim 1, wherein the porous layer comprises a plurality of nano-carbon materials, the nano-carbon materials comprising carbon nanotubes, carbon nanofibers or combinations thereof, the nano-carbon materials being stacked in an alternating manner, and the pores being located between adjacent nano-carbon materials.

6. The composite negative electrode structure according to claim 1, wherein the lithiophilic structures include silver, gold, platinum, aluminum, zinc, magnesium, silicon, tin, nickel, oxides of any of the above metals, combinations of any of the above metals and metal oxides, or organic framework materials of any of the above metals.

7. The composite negative electrode structure according to claim 1, wherein the solid electrolyte layer comprises: Lithium salts; Polymers, including polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyethylene oxide, or combinations thereof; as well as Solid electrolytes, including lithium aluminum titanium phosphate, lithium lanthanum tantalum oxide, lithium lanthanum zirconium oxide, or combinations thereof.

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