Three-dimensional structure electrode, method for manufacturing the same, and secondary battery

Abstract

This invention relates to a three-dimensional structured electrode, its fabrication method, and a secondary battery. The three-dimensional structured electrode includes a current collector, a three-dimensional conductive framework located on at least one side of the current collector, and a first active material and a second active material filling the pores of the three-dimensional conductive framework. Along the direction perpendicular to the current collector, the porosity of the three-dimensional conductive framework increases gradually away from the current collector. The three-dimensional conductive framework includes a first three-dimensional conductive framework with an average pore size P1 and a second three-dimensional conductive framework with an average pore size P2. The first three-dimensional conductive framework is closer to the current collector than the second three-dimensional conductive framework. The first active material fills the first three-dimensional conductive framework, and the second active material fills the second three-dimensional conductive framework. The three-dimensional structured electrode constructed by this invention, with functional partitioning and structural integration in three-dimensional space, effectively suppresses battery volume expansion and improves the battery's rate performance and long-cycle stability.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, and in particular to a three-dimensional structure electrode, its preparation method, and a secondary battery. Background Technology

[0002] Traditional planar coated electrodes and emerging multilayer coated electrodes are essentially two-dimensional layered stacked structures. In this structure, the lithium-ion transport path is highly tortuous, especially during high areal density and high-rate charge-discharge cycles, where concentration polarization is severe, limiting further improvements in battery performance. Furthermore, the massive volume expansion of high-capacity materials (such as silicon) during cycling can easily lead to electrode structure damage and rapid capacity decay.

[0003] Existing technologies attempt to alleviate this problem through nano-sizing, coating, or compositing with carbon materials, but these solutions fail to fundamentally address the stress accumulation and ion transport bottlenecks within the electrode structure.

[0004] Therefore, there is an urgent need for a revolutionary solution that can innovate from the three-dimensional framework level of the electrode and solve the problems of ion transport and volume expansion at the same time. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention aims to provide a three-dimensional structured electrode, its fabrication method, and a secondary battery. The three-dimensional structured electrode of this invention aims to solve the core problems of limited rate performance caused by the tortuous ion transport paths in existing two-dimensional layered electrodes, as well as electrode structure damage and poor cycle life caused by the volume expansion of high-capacity active materials. The three-dimensional structured electrode provided by this invention completely abandons the two-dimensional layered stacked structure, constructing a functional, integrated "three-dimensional interpenetrating network electrode" through 3D printing and region-selective filling technology.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a three-dimensional structure electrode, the three-dimensional structure electrode comprising a current collector, a three-dimensional conductive framework located on at least one side of the current collector, and a first active material and a second active material filling the pores of the three-dimensional conductive framework; the porosity of the three-dimensional conductive framework increases in a gradient from the current collector along the direction perpendicular to the current collector; the three-dimensional conductive framework comprises a first three-dimensional conductive framework with an average pore size P1 and a second three-dimensional conductive framework with an average pore size P2; the first three-dimensional conductive framework is closer to the current collector than the second three-dimensional conductive framework; the first active material is filled in the first three-dimensional conductive framework; and the second active material is filled in the second three-dimensional conductive framework.

[0008] The three-dimensional conductive framework of the three-dimensional structured electrode provided by this invention has vertically oriented channels and a hierarchical porous structure. Utilizing the differences in pore size and tortuosity in different regions of the three-dimensional conductive framework, high-capacity material is selectively filled into the first three-dimensional conductive framework at the bottom of the framework (near the current collector and away from the electrolyte), while high-rate material is retained in the second three-dimensional conductive framework on the surface (near the electrolyte), thus forming functional partitions. This is fundamentally different from the planar coating or layered stacked electrode structures in existing technologies.

[0009] On the other hand, the three-dimensional conductive framework in this invention provides a rapid electron transport network and mechanical support, and the vertically oriented channels shorten the ion transport path to its limit; the continuous conductive framework provides a high-speed pathway for electrons, realizing true 3D rapid transport and achieving a revolutionary improvement in rate performance. The functional materials filled in different pore sizes each perform their specific functions, fundamentally solving the inherent problems of traditional electrodes.

[0010] Compared with existing technologies, the three-dimensional structure electrode of this invention has the following essential differences and advantages in structure and composition: Difference 1 (Structural Dimension): Existing technologies, such as traditional coated electrodes or double-layer coated electrodes, are two-dimensional layered stacked structures with tortuous ion transport paths. This invention uses 3D printing technology to construct a three-dimensional continuous conductive framework with vertically oriented channels and a hierarchical porous structure, fundamentally eliminating the tortuous ion transport path. Difference 2 (Functional Zoning): Existing technologies use uniformly distributed or simply layered active materials, which cannot resolve the contradiction between the volume expansion of high-capacity materials and the rapid response of high-rate materials. This invention utilizes the pore size differences in different regions of the framework to selectively fill the bottom small pore area (near the current collector) with high-capacity materials and retain the top large pore area (near the electrolyte), achieving functional zoning in three-dimensional space, with each performing its own function and synergistically enhancing efficiency. Difference 3 (Integrated Structure): Existing composite electrodes are mostly physical mixtures of active materials and conductive agents, or fillers created using template methods, resulting in discontinuous structures. In this invention, the conductive framework itself is a continuous, integrated component, serving both as an electron transport network and a mechanical buffer layer for volume expansion, maintaining structural integrity even after the active material is filled. The advantages brought about by the above differences are mainly: ① extremely rapid ion / electron transport (shortened path in vertical channels); ② effective buffering of volume expansion (small-hole confinement effect); ③ simultaneous improvement in rate performance and cycle life.

[0011] The three-dimensional conductive skeleton provided by this invention is an integral structure. The "first" and "second" in "first three-dimensional conductive skeleton" and "second three-dimensional conductive skeleton" are only used to distinguish the pore size and indicate the regions containing pores of different sizes. They are not used to distinguish the physical structure. More clearly, "first three-dimensional conductive skeleton" represents the region of the three-dimensional conductive skeleton that is closer to the current collector, while "second three-dimensional conductive skeleton" represents the region of the three-dimensional conductive skeleton that is farther away from the current collector and closer to the surface.

[0012] This invention achieves the integration of structure and function. The three-dimensional structure electrode is a three-dimensional continuous whole, and its unique "three-dimensional skeleton + region filling" structure has never been reported in the prior art.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0014] In some embodiments, 0.1μm≤P1≤5μm, for example, can be 0.1μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm or 5μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0015] This invention further controls the average pore size P1 of the first three-dimensional conductive framework to 0.1μm≤P1≤5μm, which affects the filling effect and volume expansion buffering capacity of the high-capacity material. If P1 is too large (>5μm), the pore size of the small pore region is too large, which cannot effectively confine the high-capacity material. During charge-discharge cycles, the volume expansion of the high-capacity material will directly affect the entire framework, causing the overall electrode structure to expand, the active material to pulverize, and the SEI film to repeatedly rupture, resulting in a significant decrease in cycle life and a sharp increase in volume expansion rate. If P1 is too small (<0.1μm), the pore size is too small, and the electrolyte cannot fully wet the lithium ion, hindering lithium ion transport. At the same time, during the electrochemical deposition step, the precursor ions cannot diffuse into the interior of the small pore region, resulting in a serious lack of filling amount of the first active material, low electrode energy density, and a reduction in the electrochemical reaction interface near the current collector side, leading to a deterioration in rate performance.

[0016] In some embodiments, 5μm < P2 ≤ 50μm, for example, it can be 5.5μm, 10μm, 12μm, 15μm, 18μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm or 50μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0017] This invention further controls the average pore size P2 of the second three-dimensional conductive framework to 5μm < P2 ≤ 50μm, as this affects electrolyte wetting, ion transport rate, and electrode structural stability. If P2 is too large (> 50μm): the pore size in the macropore region is too large, the solid content of the framework decreases, mechanical strength decreases, the electron conduction path becomes longer, leading to an increase in the overall electrode resistance. Simultaneously, excessively large pores cannot effectively fix the second active material particles, which may detach during cycling, causing capacity decay. If P2 is too small (≤ 5μm): the pore size difference between the macropore and micropore regions is not significant, and an effective hierarchical structure cannot be formed. Electrolyte wetting is limited, the lithium-ion transport path becomes longer, concentration polarization is severe during high-rate charge and discharge, and rate performance drops sharply.

[0018] In this invention, the pore sizes of the first three-dimensional conductive framework (small pore region) and the second three-dimensional conductive framework (large pore region) have a synergistic relationship: (1) Functional synergy: The small pore region (0.1μm≤P1≤5μm) confines the high-capacity material near the current collector and uses the strong binding force of its nanopores to buffer the volume expansion stress; the large pore region (5μm<P2≤50μm) provides an open ion transport channel for the high-rate material, ensuring rapid electrolyte wetting and high-speed lithium ion migration. The combination of the two achieves both high energy density (contributed by high capacity materials) and high power density (contributed by high rate materials) without interference; (2) Structural synergy: The dense structure of the small pore region provides mechanical support for the electrode, while the loose structure of the large pore region provides space for ion transport. The gradient porosity design avoids the contradiction that a single pore size structure cannot balance mechanical strength and transport efficiency; (3) Process synergy: The low resistance and limited ion diffusion environment of the small pore region make good use of the "tip effect" and "diffusion control" of electrochemical deposition to achieve the self-selective bottom filling of the first active material; the large pore region is convenient for subsequent vacuum impregnation filling. The two processes do not interfere with each other and are completed in one go.

[0019] Further research and experimental verification have shown that the volume ratio of the first three-dimensional conductive framework (small-pore region) to the second three-dimensional conductive framework (large-pore region) is not fixed, but can be designed according to the energy density and power density requirements of the target battery. In a preferred embodiment, the volume ratio of the second three-dimensional conductive framework (large-pore region) to the first three-dimensional conductive framework (small-pore region) is preferably 1:2 to 2:1. When focusing on high energy density, the volume ratio of the first three-dimensional conductive framework (small-pore region) can be appropriately increased (e.g., 1:2) to accommodate more high-capacity material. When focusing on high power density, the volume ratio of the second three-dimensional conductive framework (large-pore region) can be appropriately increased (e.g., 2:1) to ensure electrolyte wetting and rapid lithium-ion transport.

[0020] In some embodiments, the first active material comprises any one or a combination of at least two of silicon, tin, antimony, aluminum, silicon suboxide, tin-based oxide, antimony-based oxide, or germanium. Typical but non-limiting combinations include combinations of silicon and tin, combinations of silicon, tin, and antimony, combinations of silicon suboxide and tin-based oxide, combinations of tin-based oxide and antimony-based oxide, combinations of silicon and germanium, and combinations of silicon, tin, antimony, and germanium.

[0021] In this invention, the first active material is a high-capacity material. The high-capacity material is confined in tiny pores at the bottom of the skeleton. Its volume expansion is absorbed and buffered by the surrounding skeleton structure, effectively avoiding damage to the overall electrode structure and greatly extending the cycle life.

[0022] In some embodiments, the second active material comprises any one or a combination of at least two of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, or lithium nickel manganese oxide. Typical but non-limiting combinations include combinations of lithium iron phosphate and lithium cobalt oxide, combinations of lithium cobalt oxide and lithium manganese oxide, combinations of lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide, combinations of lithium nickel cobalt aluminum oxide and lithium nickel manganese oxide, and combinations of lithium iron phosphate, lithium cobalt oxide, and lithium manganese oxide.

[0023] In this invention, the second active material is selected as a high-rate material (such as lithium iron phosphate, NCM, etc.) for the following reasons: Position matching: The second active material is filled in the second three-dimensional conductive framework (macropore area) near the electrolyte side, directly contacting the electrolyte, and needs to have a fast lithium insertion and extraction capability to make full use of its position advantage and achieve high-rate charging and discharging. (1) Functional complementarity: Although the first active material (high-capacity material) can provide high energy density, its rate performance and cycle stability are poor; the second active material (high-rate material) has excellent rate performance and stable structure, but its specific capacity is low; (2) The two are filled in three-dimensional space to achieve the synergistic configuration of "high-capacity buried bottom and high-rate surface layer": When the rate is low or when it is stationary, lithium ions can diffuse to the bottom and react with the high-capacity material to store more energy; when the rate is high, the surface high-rate material responds quickly and provides instantaneous large current; when charging, the surface material quickly accepts lithium ions and avoids lithium plating. (3) Volume expansion isolation: The volume expansion of the high-capacity material is restricted to the bottom small hole area, which will not damage the structural integrity of the surface high-rate material and ensure the overall stability of the electrode in long cycles.

[0024] In some embodiments, the three-dimensional conductive framework comprises a conductive material.

[0025] In some embodiments, the conductive material includes carbon materials, metallic materials, or composite materials of carbon and metallic materials.

[0026] In some embodiments, the carbon material includes any one or a combination of at least two of graphene, carbon nanotubes, carbon fibers, Ketjen black, acetylene black, or mesoporous carbon. Typical but non-limiting combinations include combinations of graphene and carbon nanotubes, combinations of carbon nanotubes and carbon fibers, and combinations of graphene and Ketjen black.

[0027] In some embodiments, the metallic material includes any one or a combination of at least two of nickel, copper, aluminum, stainless steel, or titanium. Typical but non-limiting combinations include combinations of nickel and copper, aluminum and stainless steel, copper and aluminum, aluminum and titanium, and nickel, aluminum, and stainless steel.

[0028] In some embodiments, the average thickness of the three-dimensional conductive framework is 50μm-300μm, for example, it can be 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 120μm, 150μm, 180μm, 200μm, 220μm, 250μm, 280μm or 300μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0029] In a second aspect, the present invention provides a method for preparing a three-dimensional structure electrode as described in the first aspect, the method comprising the following steps:

[0030] The three-dimensional conductive framework is immersed in the first active material precursor slurry, and the first active material is filled into the first three-dimensional conductive framework by electrochemical deposition; the second active material slurry is introduced into the second three-dimensional conductive framework to obtain the three-dimensional structure electrode.

[0031] This invention employs an electrochemical deposition method to fill a first active material into a three-dimensional conductive framework with an average pore size of P1. Since the resistance of the small pore area at the bottom of the three-dimensional conductive framework is low and ion diffusion is restricted, the deposition reaction preferentially occurs in this area, thereby selectively filling the bottom of the framework (near the current collector side) with the first active material, thus reserving a large pore size of P2 for the filling of the second active material, achieving stepwise filling.

[0032] The selective mechanism of electrochemical deposition in this invention is as follows: (1) Resistance difference: The small pores at the bottom of the three-dimensional conductive framework (near the current collector) have a dense structure, short electron transport paths, and low resistance; the large pores at the top have a loose structure and relatively high resistance. When the same potential is applied, the current density in the small pores at the bottom is greater, and the electrochemical reaction occurs preferentially; (2) Diffusion restriction: The pore size of the first three-dimensional conductive framework is small (0.1μm≤P1≤5μm), which hinders ion diffusion and forms a local concentration gradient. Precursor ions (such as silane and tin salt) migrate slowly in the pores. Once consumed at the bottom, they are difficult to replenish quickly from the outside, thus forming a stable deposition at the bottom. In contrast, the ion diffusion in the large pores is unobstructed, and preferential deposition is not easy to occur; (3) Nucleation barrier difference: The inner wall of the small pores has more active sites and higher curvature, which reduces the overpotential for electrochemical nucleation and promotes preferential nucleation and growth.

[0033] Existing technologies typically employ template-based pore creation followed by overall impregnation or coating, which fails to achieve selective distribution of active materials in three-dimensional space; or they utilize complex processes such as mask lithography, resulting in high costs and low efficiency. This invention, however, utilizes the inherent structural characteristics of the three-dimensional framework (pore size gradient, resistance gradient) to achieve self-selective filling. Without the need for additional masks or complex processes, a single electrochemical deposition step can precisely position high-capacity materials in the bottom pore region. The process is simple, low-cost, and suitable for mass production.

[0034] In some embodiments, the three-dimensional conductive framework is obtained using the following preparation method:

[0035] (a) A slurry is obtained by mixing conductive materials, polymer monomers and initiators. According to the designed three-dimensional structural model, the slurry is printed on the surface of at least one side of the current collector using 3D printing technology to form a three-dimensional skeleton.

[0036] (b) The three-dimensional skeleton is post-processed and activated to obtain the three-dimensional conductive skeleton.

[0037] This invention uses 3D printing technology to construct an integrated skeleton with functional partitions in three-dimensional space. The purpose of post-processing the three-dimensional skeleton is to remove the organic template in the skeleton, and then activate the conductive material to obtain a pure three-dimensional conductive skeleton.

[0038] In this invention, the three-dimensional skeleton formed by 3D printing is post-processed and activated through heat treatment or chemical reduction methods. The organic polymer template (such as polyethylene glycol diacrylate) is removed by pyrolysis or chemical decomposition. During pyrolysis, the carbonization of organic components may leave a small amount of amorphous carbon. This residual carbon not only does not affect the purity of the skeleton but also helps to enhance the electronic conductivity and structural mechanical strength of the conductive skeleton. Therefore, in the final three-dimensional conductive skeleton, the organic template has been largely removed, and the skeleton mainly consists of conductive materials (such as reduced graphene oxide, carbon nanotubes, etc.) and possibly trace amounts of pyrolytic carbon.

[0039] In some embodiments, the 3D printing process includes digital light processing or direct writing.

[0040] In some embodiments, the polymer monomer includes thermosetting resins and / or photocurable resins.

[0041] In some embodiments, the thermosetting resin includes any one or a combination of at least two of epoxy resin, phenolic resin, or polyurethane.

[0042] In some embodiments, the photocurable resin includes any one or a combination of at least two of polyethylene glycol diacrylate (PEGDA), polyethylene glycol dimethacrylate (PEGDMA), trimethylolpropane triacrylate (TMPTA), or pentaerythritol triacrylate (PETA).

[0043] In some embodiments, the initiator includes a photoinitiator and / or a thermal initiator.

[0044] In some embodiments, the photoinitiator includes any one or a combination of at least two of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (photoinitiator 819), 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), and 1-hydroxycyclohexylphenyl ketone (184).

[0045] In some embodiments, the thermal initiator includes azobisisobutyronitrile (AIBN) and / or benzoyl peroxide (BPO).

[0046] In some embodiments, the mass ratio of the conductive material to the polymer monomer is 1:(0.1-2), preferably 1:(0.8-1.2), for example, it can be 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.5, 1:1.8, 1:1.9 or 1:2, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0047] This invention controls the mass ratio of the conductive material to the polymer monomer to be 1:(0.1-2), ensuring both good printable rheology and curing properties of the slurry, as well as the integrity and conductivity of the conductive framework after post-processing. If the proportion of conductive material is too high: the slurry viscosity is too high, resulting in poor flowability and making DLP printing difficult; the framework becomes more brittle after curing. If the proportion of conductive material is too low: there are too many organic components after curing; after removing the organic matter in post-processing, the conductive network may collapse due to insufficient support, or the conductive material may not be tightly connected, leading to decreased conductivity. The preferred range for the amount of initiator added relative to the total mass of the slurry in this invention is 0.5wt% to 2wt%. If the amount added is too low (<0.5wt%): the photocuring reaction is incomplete, resulting in insufficient strength of the printed green body and easy deformation. If the amount added is too high (>2wt%): excessive free radicals may be generated, leading to an overly rapid polymerization reaction, increased internal stress, and also causing cracking of the green body; at the same time, residual initiator may be difficult to remove completely in post-processing, affecting material purity.

[0048] In some embodiments, the post-processing method includes heat treatment and / or chemical reduction.

[0049] In some embodiments, the heat treatment atmosphere is an inert atmosphere.

[0050] In some embodiments, the heat treatment temperature is 250°C-350°C, for example, it can be 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C or 350°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0051] In some embodiments, the heat treatment time is 1h-5h, for example, it can be 1h, 2h, 3h, 4h or 5h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0052] In some embodiments, the activation method includes reduction.

[0053] In some embodiments, the first active material precursor slurry includes a first active material precursor and an electrolyte.

[0054] In some embodiments, the first active material precursor includes any one or a combination of at least two of trichlorosilane, silicon tetrachloride, silane, tin salt, or antimony salt.

[0055] In some embodiments, the electrolyte comprises an ionic liquid and / or an organic solvent.

[0056] In some embodiments, the ionic liquid comprises 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM]TFSI) and / or 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6).

[0057] In some embodiments, the organic solvent includes any one or a combination of at least two of propylene carbonate, acetonitrile, or tetrahydrofuran. Typical but non-limiting combinations include combinations of propylene carbonate and acetonitrile, combinations of acetonitrile and tetrahydrofuran, combinations of propylene carbonate and tetrahydrofuran, and combinations of propylene carbonate, acetonitrile, and tetrahydrofuran.

[0058] In some embodiments, the electrochemical deposition is constant potential deposition, constant current deposition, or pulsed electrodeposition, preferably constant potential deposition.

[0059] In some embodiments, the voltage magnitude of the electrochemical deposition is -1.5V to -1.2V (relative to Ag / Ag). + The reference electrode can be, for example, -1.5V, -1.45V, -1.4V, -1.35V, -1.3V, -1.25V, or -1.2V, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0060] This invention further controls the voltage of the electrochemical deposition to -1.5V to -1.2V (relative to Ag / Ag). + The voltage of electrochemical deposition (reference electrode) affects the deposition rate, morphology, and selectivity of the first active material. Excessive voltage and overpotential result in a rapid deposition rate, leading to a loose, dendritic layer and preventing the formation of a dense, uniform filling layer. Furthermore, excessively high voltage may trigger side reactions (such as electrolyte decomposition and hydrogen evolution), reducing deposition efficiency and material purity, and impairing electrode performance. Conversely, insufficient voltage and overpotential result in inadequate electrochemical driving force, making deposition reactions difficult or extremely slow, leading to insufficient filling of the first active material and low electrode energy density. Additionally, selective filling deteriorates, and some active material may deposit in the macroporous region, disrupting the functional zoning design.

[0061] In some embodiments, the electrochemical deposition time is 20 min to 40 min, for example, 20 min, 25 min, 30 min, 35 min or 40 min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0062] In some embodiments, the second active material slurry includes a second active material, a conductive agent, a binder, and a solvent.

[0063] In some embodiments, the mass ratio of the second active material, the conductive agent, and the binder is (90-98):(1-5):(1-5), for example, it can be 92:4:4, 93:3:4, 94:3:3, 95:2:3, 95:3:2, 96:2:2, 97:1:2, 97:2:1, 97:1.5:1.5, 97.5:1.5:1, or 98:1:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0064] In some embodiments, the present invention does not limit the specific type of conductive agent. Exemplarily, the conductive agent includes any one or a combination of at least two of Super P, acetylene black, Ketjen black, carbon nanotubes, graphene, artificial graphite, or vapor-grown carbon fiber (VGCF). Typical but non-limiting combinations include combinations of Super P and acetylene black, combinations of Ketjen black and carbon nanotubes, combinations of carbon nanotubes and graphene, combinations of artificial graphite and vapor-grown carbon fiber, combinations of Super P, acetylene black, and carbon nanotubes, combinations of graphene, artificial graphite, and vapor-grown carbon fiber, or combinations of Ketjen black, carbon nanotubes, and graphene.

[0065] In this invention, when the conductive agent is a combination of GO and CNT, the mass ratio of GO to CNT is more preferably 1:(0.5-2). By adjusting the ratio of GO to CNT, GO helps to disperse and regulate rheological properties, while CNT helps to build an efficient electron transport network. The synergistic effect of the two is the key to ensuring the performance of the skeleton.

[0066] In some embodiments, the present invention does not limit the specific type of adhesive. Exemplarily, the adhesive includes any one or a combination of at least two of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyimide (PI), polyvinyl alcohol (PVA), or sodium alginate. Typical but non-limiting combinations include combinations of polyvinylidene fluoride and sodium carboxymethyl cellulose, combinations of styrene-butadiene rubber and polytetrafluoroethylene, combinations of polyacrylic acid and polyimide, combinations of polyvinyl alcohol and sodium alginate, combinations of polyvinylidene fluoride and polypropylene, and combinations of sodium carboxymethyl cellulose, polyvinyl alcohol, and sodium alginate.

[0067] In some embodiments, the present invention does not limit the specific type of solvent. Exemplarily, the solvent includes any one or a combination of at least two of water, NMP, DMF, or ethylene glycol. Typical but non-limiting combinations include combinations of NMP and DMF, water and ethylene glycol, DMF and ethylene glycol, and water, NMP, and DMF.

[0068] In some embodiments, the introduced method includes vacuum-assisted impregnation and / or blade coating.

[0069] This invention employs methods such as vacuum-assisted impregnation or scraping to fill the remaining macropores on the surface of the framework with a slurry containing a second active material. This method allows the active material slurry to fully penetrate every corner of the second three-dimensional conductive framework (macropore area) under negative pressure, resulting in a more uniform and dense filling. After drying and rolling, the active material is tightly bonded to the framework, forming an integral electrode structure with a certain mechanical strength.

[0070] In some embodiments, after introducing the second active material slurry into the second three-dimensional conductive framework with an average pore size of P2 and before obtaining the three-dimensional structure electrode, the process further includes drying and rolling.

[0071] As a preferred embodiment of the preparation method of the present invention, the preparation method includes the following steps:

[0072] (1) A slurry is obtained by mixing conductive materials, polymer monomers and initiators. According to the designed three-dimensional structural model, the slurry is printed on the surface of at least one side of the current collector to form a three-dimensional skeleton.

[0073] (2) The three-dimensional framework obtained in step (1) is subjected to heat treatment and / or chemical reduction, and then reduced activation is performed to obtain a three-dimensional conductive framework; the three-dimensional conductive framework includes a first three-dimensional conductive framework with an average pore size of P1 and a second three-dimensional conductive framework with an average pore size of P2, wherein 0.1μm≤P1≤5μm, 5μm<P2≤50μm;

[0074] (3) Immerse the three-dimensional conductive framework obtained in step (2) into the first active material precursor slurry and perform electrochemical deposition at -1.5V to -1.2V for 20min-40min to fill the first active material into the first three-dimensional conductive framework.

[0075] The first active material precursor slurry includes a first active material and an electrolyte;

[0076] (4) Subsequently, the second active material slurry is introduced into the second three-dimensional conductive skeleton with an average pore size of P2 by vacuum-assisted impregnation and / or scraping method, and after drying and rolling, the three-dimensional structure electrode is obtained.

[0077] The second active material slurry includes a solvent and a second active material, a conductive agent, and a binder in a mass ratio of (90-98):(1-5):(1-5).

[0078] Thirdly, the present invention provides a secondary battery, the secondary battery comprising the three-dimensional structure electrode described in the first aspect.

[0079] The secondary battery provided by this invention has excellent rate performance and long-term cycle stability. Its capacity retention rate can reach 96.5% after 200 cycles at 0.5C, and its volume expansion rate is only 18% after 100 cycles, which effectively suppresses the volume expansion of the battery.

[0080] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0081] Compared with the prior art, the present invention has at least the following beneficial effects:

[0082] (1) The three-dimensional structure electrode provided by this invention utilizes the differences in pore size and tortuosity in different regions of the three-dimensional conductive framework to selectively fill the micropore P1 region at the bottom of the framework (near the current collector and away from the electrolyte) with high-capacity material, while retaining the high-rate material in the larger channels P2 on the surface of the framework (near the electrolyte), thereby forming functional zones. The three-dimensional conductive framework provides a fast electron transport network and mechanical support. The continuous conductive framework provides a high-speed pathway for electrons, realizing true 3D fast transport. The functional materials filled in different pore sizes perform their respective functions, fundamentally solving the inherent problems of traditional electrodes.

[0083] (2) The present invention uses electrochemical deposition to fill the first active material into the first three-dimensional conductive framework with an average pore size of P1. Since the resistance of the small pore area at the bottom of the three-dimensional conductive framework is low and the ion diffusion is restricted, the deposition reaction occurs preferentially in this area, thereby selectively filling the first active material at the bottom of the framework (near the current collector side), thus reserving a large pore size of P2 for the filling of the second active material, and realizing step-by-step filling.

[0084] (3) The secondary battery provided by the present invention has excellent rate performance and long cycle stability. Its capacity retention rate can reach 96.5% after 200 cycles at 0.5C, and its volume expansion rate is only 18% after 100 cycles, which effectively suppresses the volume expansion of the battery. Attached Figure Description

[0085] Figure 1 This is a schematic diagram of the cross-sectional structure of the three-dimensional structure electrode provided in Embodiment 1 of the present invention, wherein 1-current collector; 2-second three-dimensional conductive framework; 3-first active material; 4-second three-dimensional conductive framework; 5-second active material. Detailed Implementation

[0086] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0087] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0088] In this invention, "a combination of at least two" refers to a quantity greater than or equal to 2 unless otherwise specified. For example, "any one or a combination of at least two" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention. In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. The arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" means a set consisting of A, B, and combinations of A and B, where "containing A and / or B" can be understood, depending on the context of the statement, as containing A, containing B, or simultaneously containing both A and B. In this invention, "optional" means that the corresponding feature, component, step or solution is not necessary, that is, it is selected from either "with" or "without". If there are multiple "optional" limitations in a technical solution, unless otherwise specified and there is no technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0089] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A can consist only of a1, a2, and a3, or it can include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements." All embodiments and optional embodiments of this invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various locations throughout the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this invention can be combined with other embodiments that do not conflict with the technology. The ordinal numbers "first," "second," "third," and "fourth," etc., used in the expressions "first aspect," "second aspect," "third aspect," and "fourth aspect" in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0090] In this invention, the order in which the steps are written in the methods described in each embodiment does not imply a strict execution order. The actual execution order of each step should be determined based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any order without conflict, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0091] Unless otherwise specified, all reagents and consumables used in the following examples and comparative examples were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used were conventional methods and techniques in the art.

[0092] Example 1

[0093] This embodiment provides a three-dimensional structured electrode, the structural schematic of which is shown below. Figure 1 As shown, it should be noted that the interfaces in the schematic diagram are only for distinguishing different areas and do not represent the actual three-dimensional conductive framework. The actual three-dimensional conductive framework does not have any distinguishable interlayer physical interfaces; the porosity increases gradually away from the current collector, and is a continuous, seamless change. The three-dimensional structure electrode includes a current collector 1, a three-dimensional conductive framework located on at least one side of the current collector, and a first active material silicon 3 and a second active material lithium iron phosphate 5 filling the pores of the three-dimensional conductive framework.

[0094] The three-dimensional conductive framework includes a first three-dimensional conductive framework 2 with an average pore size P1 of 2 μm and a second three-dimensional conductive framework 4 with an average pore size P2 of 15 μm; the first three-dimensional conductive framework is closer to the current collector than the second three-dimensional conductive framework; the vertical arrow in the figure (the arrow points from the current collector to the electrode surface) indicates the direction of rapid transport of lithium ions along the vertically oriented channels, and the continuous three-dimensional conductive framework provides a high-speed pathway for electrons.

[0095] The method for fabricating the three-dimensional structure electrode provided in this embodiment includes the following steps:

[0096] (1) Graphene oxide (GO), carbon nanotubes (CNT) and polyethylene glycol diacrylate (PEGDA 600) were mixed in a mass ratio of 1:1:8, and phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (photoinitiator 819) was added to prepare a photocurable slurry. According to the designed three-dimensional structure model, the photocurable slurry was printed on at least one side of the copper foil using 3D printing technology to form a three-dimensional skeleton.

[0097] (2) The three-dimensional framework obtained in step (1) is heat-treated at 300°C for 2 hours under an inert atmosphere to remove organic matter and simultaneously reduce graphene oxide to obtain the three-dimensional conductive framework.

[0098] (3) The three-dimensional conductive framework obtained in step (2) is immersed in a precursor slurry of trichlorosilane and ionic liquid [EMIM]TFSI and electrochemically deposited at -1.5V for 30 min to fill silicon in the first three-dimensional conductive framework (small hole region) with an average pore size of 2μm.

[0099] (4) The second active material slurry is then filled into the second three-dimensional conductive skeleton with an average pore size of P2 by vacuum-assisted impregnation. After drying and rolling, the three-dimensional structure electrode is obtained.

[0100] The second active material slurry is an aqueous slurry prepared by mixing nano lithium iron phosphate (LFP), Super P and CMC in a ratio of 95:2:3.

[0101] Example 2

[0102] This embodiment provides a three-dimensional structure electrode, which includes a current collector, a three-dimensional conductive framework located on at least one side of the current collector, and a first active material silicon and a second active material lithium iron phosphate filling the pores of the three-dimensional conductive framework.

[0103] The three-dimensional conductive framework includes a first three-dimensional conductive framework with an average pore size P1 of 1 μm and a second three-dimensional conductive framework with an average pore size P2 of 10 μm; the first three-dimensional conductive framework is closer to the current collector than the second three-dimensional conductive framework.

[0104] The method for fabricating the three-dimensional structure electrode provided in this embodiment includes the following steps:

[0105] (1) A slurry is obtained by mixing conductive materials (graphene oxide and carbon nanotubes in a mass ratio of 1:1), polymer monomers (PEGDA600) and initiator 819, wherein the mass ratio of conductive materials to polymer monomers is 1:0.8. According to the designed three-dimensional structural model, the slurry is printed on the surface of at least one side of the current collector using 3D printing technology to form a three-dimensional skeleton.

[0106] (2) The three-dimensional skeleton obtained in step (1) is heat-treated at 250°C for 3 hours in an inert atmosphere to remove organic matter and reduce it, thereby obtaining the three-dimensional conductive skeleton.

[0107] (3) Immerse the three-dimensional conductive framework obtained in step (2) into the first active material precursor slurry and perform electrochemical deposition at -1.3V for 25 min to fill the first active material into the first three-dimensional conductive framework with an average pore size of P1.

[0108] The first active material precursor slurry includes a first active material and an electrolyte;

[0109] (4) Subsequently, the second active material slurry is introduced into the second three-dimensional conductive skeleton with an average pore size of P2 by vacuum-assisted impregnation and / or scraping method, and after drying and rolling, the three-dimensional structure electrode is obtained.

[0110] The second active material slurry comprises water and lithium iron phosphate (a second active material) in a mass ratio of 96:2:2, conductive agent Super P, and binder CMC.

[0111] Example 3

[0112] This embodiment provides a three-dimensional structure electrode, which includes a current collector, a three-dimensional conductive framework located on at least one side of the current collector, and a first active material silicon and a second active material lithium iron phosphate filling the pores of the three-dimensional conductive framework.

[0113] The three-dimensional conductive framework includes a first three-dimensional conductive framework with an average pore size P1 of 5 μm and a second three-dimensional conductive framework with an average pore size P2 of 45 μm; the first three-dimensional conductive framework is closer to the current collector than the second three-dimensional conductive framework.

[0114] The method for fabricating the three-dimensional structure electrode provided in this embodiment includes the following steps:

[0115] (1) Graphene oxide (GO), carbon nanotubes (CNT) and polyethylene glycol diacrylate (PEGDA 600) were mixed in a mass ratio of 1:1:8, and phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (photoinitiator 819) was added to prepare a photocurable slurry. According to the designed three-dimensional structural model, the slurry was printed on the surface of at least one side of the current collector to form a three-dimensional skeleton using 3D printing technology.

[0116] (2) The three-dimensional skeleton obtained in step (1) is heat-treated at 350°C for 1 hour in an inert atmosphere to remove organic matter and reduce it, thereby obtaining the three-dimensional conductive skeleton.

[0117] (3) Immerse the three-dimensional conductive framework obtained in step (2) into the first active material precursor slurry and perform electrochemical deposition at -1.2V for 40 min to fill the first active material into the first three-dimensional conductive framework with an average pore size of P1.

[0118] The first active material precursor slurry includes a first active material and an electrolyte;

[0119] (4) Subsequently, the second active material slurry is introduced into the second three-dimensional conductive skeleton with an average pore size of P2 by vacuum-assisted impregnation and / or scraping method, and after drying and rolling, the three-dimensional structure electrode is obtained.

[0120] The second active material slurry is an aqueous slurry prepared by mixing nano lithium iron phosphate (LFP), Super P and CMC in a ratio of 95:2:3.

[0121] Example 4

[0122] This embodiment provides a three-dimensional structure electrode. The only difference from Embodiment 1 is that, in the preparation of this three-dimensional structure electrode, the average pore size P1 of the first three-dimensional conductive skeleton is 10 μm during the 3D printing process in step (1), while the other steps remain unchanged.

[0123] Example 5

[0124] This embodiment provides a three-dimensional structure electrode. The only difference from Embodiment 1 is that, in the preparation of this three-dimensional structure electrode, the average pore size P2 of the second three-dimensional conductive skeleton is 3μm during the 3D printing process in step (1), while the other steps remain unchanged.

[0125] Example 6

[0126] This embodiment provides a three-dimensional structure electrode. The only difference from Embodiment 1 is that, in the preparation of this three-dimensional structure electrode, the average pore size P2 of the second three-dimensional conductive skeleton is 100 μm during the 3D printing process in step (1), while the other steps remain unchanged.

[0127] Example 7

[0128] This embodiment provides a three-dimensional structure electrode. The only difference from Embodiment 1 is that when preparing the three-dimensional structure electrode, the voltage of electrochemical deposition in step (2) is -2V, and the other steps remain unchanged.

[0129] Example 8

[0130] This embodiment provides a three-dimensional structure electrode. The only difference from Embodiment 1 is that when preparing the three-dimensional structure electrode, the voltage of electrochemical deposition in step (2) is -1V, and the other steps remain unchanged.

[0131] Comparative Example 1

[0132] This comparative example provides a single-layer planar electrode, which is prepared by the following method:

[0133] NCM811, Super P, and PVDF were mixed in a ratio of 96:2:2 to form a slurry, which was then coated onto aluminum foil and dried to obtain a conventional single-layer flat electrode.

[0134] Comparative Example 2

[0135] This comparative example provides a double-layer electrode, which is prepared by the following method:

[0136] Preparation of the first positive electrode active material layer slurry: Polycrystalline NCM622 active material (D50=10μm), conductive carbon black, carbon nanotubes (CNT), and PVDF were dissolved in NMP at a mass ratio of 96.5:1.5:0.5:1.5 and stirred evenly to prepare the first slurry.

[0137] Preparation of the second positive electrode active material layer slurry: Single crystal NCM622 active material (D50=4μm), conductive carbon black, and PVDF are dissolved in NMP at a mass ratio of 97.5:1.5:1.0 and stirred evenly to prepare the second slurry.

[0138] Coating: A double-layer coating machine is used. First, a first slurry is coated on a 12μm thick aluminum foil, controlling the dry film thickness to 50μm. After drying, a second slurry is coated on the surface of the first layer, controlling the dry film thickness to 10μm.

[0139] Drying and Rolling: After two coatings, a final drying process is performed at a temperature of 100-120℃. Following drying, the material is rolled to achieve a compaction density of 3.3 g / cm³. 3 .

[0140] Comparative Example 3

[0141] This comparative example provides an electrode, which differs from Example 1 only in that, during the preparation of this electrode, in step (1) of the 3D printing process, the pore size in the three-dimensional skeleton is P1=P2=2μm, that is, the porosity of the conductive skeleton is uniformly distributed along the direction perpendicular to the current collector and the pore size is equal, and the rest of the preparation method remains unchanged.

[0142] Comparative Example 4

[0143] This comparative example provides an electrode that differs from Example 1 only in that, when preparing the electrode, the second active material lithium iron phosphate in step (4) is replaced with silicon, which is the same as the first and second active materials and is not divided into regions.

[0144] test:

[0145] Structural characterization: The morphology and elemental distribution of the electrode cross section were analyzed by SEM and X-ray energy dispersive spectroscopy (EDS).

[0146] Cycling performance: Using the electrodes provided in the examples and comparative examples as positive electrodes (or negative electrodes, depending on the electrode type), lithium metal sheets as counter electrodes, and a mixed solvent of 1M LiPF6 dissolved in ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio 1:1) as electrolyte, 2032 coin half-cells were assembled and cycled at 0.5C rate, and the capacity retention rate was recorded after 200 cycles.

[0147] Rate performance: tested discharge capacity from 0.2C to 5C.

[0148] Volumetric expansion rate: After 100 cycles, the change in electrode thickness was measured by SEM, and the volumetric expansion rate was calculated. The test results are shown in Table 1 below.

[0149] Table 1

[0150]

[0151] The test results show that:

[0152] (1) As can be seen from Examples 1-3, the present invention constructs an integrated three-dimensional structure electrode with functional partitions in three-dimensional space through 3D printing and area selective filling technology. The electrode selectively fills the micropore P1 region at the bottom of the skeleton with high-capacity material (close to the current collector and away from the electrolyte), and retains the high-rate material in the larger pores P2 on the surface of the skeleton (close to the electrolyte), thereby forming functional partitions; the three-dimensional conductive skeleton provides a fast electron transport network and mechanical support, and the continuous conductive skeleton provides a high-speed path for electrons, realizing true 3D fast transport. The functional materials filled in different pore sizes perform their respective functions, thereby effectively suppressing the volume expansion of the battery and improving the rate performance and long-cycle stability of the battery.

[0153] (2) A comparison between Example 1 and Example 4 shows that by further controlling 0.1μm≤P1≤5μm, the average pore size P1 of the first three-dimensional conductive framework in the present invention affects the confinement effect of the high-capacity material. When P1 is too large (10μm, Example 4), the small pore area cannot effectively buffer the volume expansion of silicon, resulting in a capacity retention rate of 88.5% and a volume expansion rate of 32.0% after 200 cycles, which is far worse than Example 1 (96.5%, 18.0%). If P1 is too small (<0.1μm), electrolyte wetting and ion transport are hindered. Although not directly given in the examples, this principle will lead to insufficient filling and a decrease in rate performance.

[0154] (3) A comparison of Examples 1 and Examples 5-6 shows that by further controlling 5μm < P2 ≤ 50μm, the average pore size P2 of the second three-dimensional conductive framework affects ion transport and rate performance. When P2 is too small (3μm, Example 5), ion transport in the macropore region is limited, and the 5C capacity retention rate drops to 70.0%; when P2 is too large (100μm, Example 6), the mechanical strength of the framework decreases, the 5C capacity retention rate drops to 75.0%, and the cycle retention rate also drops to 90.0%. Both are significantly worse than Example 1 (92.0%, 96.5%).

[0155] (4) A comparison between Example 1 and Examples 7-8 shows that the present invention further controls the voltage of electrochemical deposition to -1.5V to -1.2V. When the voltage is too high (-2V, Example 7), the deposition rate is too fast, the silicon layer is loose and uneven, resulting in a cycle retention rate of 85.0% and a volume expansion rate of 30.0%. When the voltage is too low (-1V, Example 8), the deposition driving force is insufficient, the silicon filling amount is small, and although the volume expansion is small (15.0%), the capacity and rate performance are significantly reduced (5C retention rate 72.0%, cycle retention rate 80.0%). Only a suitable voltage range can achieve uniform, sufficient and selective filling.

[0156] (5) As can be seen from Example 1 and Comparative Examples 1-2, the present invention achieves rate performance and cycle stability far superior to traditional flat plate and double-layer coated electrodes by constructing a three-dimensional interpenetrating network structure, while effectively suppressing volume expansion. Its unique structure and preparation method significantly improve the electrochemical performance of the battery.

[0157] (6) As can be seen from Example 1 and Comparative Examples 3-4, the present invention achieves the effect of effectively suppressing battery volume expansion and improving battery long-cycle stability by constructing a "three-dimensional conductive framework + regional filling of active material". However, when the three-dimensional conductive framework is not prepared or the active material is not regionally filled, the effect is far inferior to that of the present application.

[0158] In summary, this invention utilizes 3D printing and region-selective filling technology to construct an integrated three-dimensional electrode structure with functional partitions in three-dimensional space. This electrode selectively fills the microporous region P1 at the bottom of the framework (near the current collector and away from the electrolyte) with high-capacity material, while retaining high-rate material in the larger channels P2 on the surface of the framework (near the electrolyte), thus forming functional partitions. The three-dimensional conductive framework provides a rapid electron transport network and mechanical support; the continuous conductive framework provides a high-speed pathway for electrons, achieving true 3D rapid transport. The functional materials filled in different pore sizes perform their respective functions, effectively suppressing battery volume expansion and improving the battery's rate performance and long-cycle stability.

[0159] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A three-dimensional structured electrode, characterized by, The three-dimensional structure electrode comprises a current collector, a three-dimensional conductive framework on at least one side of the current collector, and a first active material and a second active material filled in the pores of the three-dimensional conductive framework; In the direction perpendicular to the current collector, the porosity of the three-dimensional conductive framework increases in the direction away from the current collector; The three-dimensional conductive framework comprises a first three-dimensional conductive framework with an average pore size of P1 and a second three-dimensional conductive framework with an average pore size of P2; the first three-dimensional conductive framework is closer to the current collector than the second three-dimensional conductive framework; The first active material is filled in the first three-dimensional conductive framework; The second active material is filled in the second three-dimensional conductive framework.

2. The three-dimensional structured electrode according to claim 1, wherein 0.1 μm≤P1≤5 μm; And / or, 5 μm 3. The three-dimensional structured electrode according to claim 1, wherein The first active material comprises any one or a combination of at least two of silicon, tin, antimony, aluminum, silicon monoxide, tin-based oxide, antimony-based oxide, or germanium; And / or, the second active material comprises any one or a combination of at least two of lithium iron phosphate, lithium cobaltate, lithium manganate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, or lithium nickel manganate.

4. The three-dimensional structured electrode according to claim 1, wherein The three-dimensional conductive framework comprises a conductive material; And / or, the conductive material comprises a carbon material, a metal material, or a composite material of the carbon material and the metal material; And / or, the average thickness of the three-dimensional conductive framework is 50 μm-300 μm.

5. A method of producing a three-dimensional structure electrode as claimed in any one of claims 1 to 4, characterized by, The preparation method comprises the following steps: immersing the three-dimensional conductive framework into a first active material precursor slurry, electrochemically depositing the first active material into the first three-dimensional conductive framework, introducing a second active material slurry into the second three-dimensional conductive framework to obtain the three-dimensional structure electrode.

6. The production method according to claim 5, wherein The three-dimensional conductive framework is obtained by the following preparation method: (a) mixing a conductive material, a polymer monomer, and an initiator to obtain a slurry, printing the slurry on the surface of at least one side of the current collector according to a designed three-dimensional structure model by a 3D printing process to form a three-dimensional framework; (b) post-treating and activating the three-dimensional framework to obtain the three-dimensional conductive framework.

7. The preparation method according to claim 6, characterized in that, The 3D printing process comprises a digital light processing method or a direct writing forming method; And / or, the post-treatment method comprises heat treatment and / or chemical reduction; And / or, the activation method comprises reduction.

8. The preparation method according to claim 5, characterized in that, The first active material precursor slurry comprises a first active material precursor and an electrolyte; And / or, the voltage of the electrochemical deposition is-1.5 V to-1.2 V; And / or, the time of the electrochemical deposition is 20 min-40 min; And / or, the second active material slurry comprises a second active material, a conductive agent, a binder, and a solvent; And / or, the mass ratio of the second active material, the conductive agent, and the binder is (90-98):(1-5):(1-5); And / or, the introduction method comprises a vacuum-assisted impregnation method and / or a doctor blade method; And / or, after introducing the second active material slurry into the second three-dimensional conductive framework with an average pore size of P2, the method further comprises drying and rolling before obtaining the three-dimensional structure electrode.

9. The preparation method according to claim 5, characterized in that, The preparation method comprises the following steps: (1) A slurry is obtained by mixing conductive materials, polymer monomers and initiators. According to the designed three-dimensional structural model, the slurry is printed on the surface of at least one side of the current collector to form a three-dimensional skeleton. (2) The three-dimensional framework obtained in step (1) is subjected to heat treatment and / or chemical reduction, and then reduced activation to obtain a three-dimensional conductive framework; the three-dimensional conductive framework includes a first three-dimensional conductive framework with an average pore size of P1 and a second three-dimensional conductive framework with an average pore size of P2, wherein 0.1μm≤P1≤5μm, 5μm<P2≤50μm; the first three-dimensional conductive framework is closer to the current collector than the second three-dimensional conductive framework; (3) Immerse the three-dimensional conductive framework obtained in step (2) into the first active material precursor slurry and perform electrochemical deposition at -1.5V to -1.2V for 20min-40min to fill the first active material into the first three-dimensional conductive framework with an average pore size of P1. The first active material precursor slurry includes a first active material and an electrolyte; (4) Subsequently, the second active material slurry is introduced into the second three-dimensional conductive skeleton with an average pore size of P2 by vacuum-assisted impregnation and / or scraping method, and after drying and rolling, the three-dimensional structure electrode is obtained. The second active material slurry includes a solvent and a second active material, a conductive agent, and a binder in a mass ratio of (90-98):(1-5):(1-5).

10. A secondary battery characterized by comprising: The secondary battery includes the three-dimensional structure electrode as described in any one of claims 1-4.

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