A non-negative electrode lithium ion battery and a preparation method thereof

Abstract

This invention relates to a negative electrode-free lithium-ion battery and its preparation method. The preparation method includes: mixing and stirring a high-nickel ternary active material, a conductive agent, and a binder to fibrousize the binder, obtaining a mixed powder; hot-rolling the mixed powder to obtain a self-supporting electrode film; hot-pressing the self-supporting electrode film with a carbon-coated aluminum foil current collector to obtain a positive electrode sheet; lithiophilizing the copper foil current collector to obtain a negative electrode sheet with a lithiophilic gradient modification layer; stacking the positive electrode sheet, negative electrode sheet, and separator into a battery cell; injecting a prepared electrolyte; vacuum sealing and allowing it to stand to obtain a negative electrode-free lithium-ion battery. This preparation method constructs a low-torsion directional ion channel on the positive electrode side and simultaneously constructs a gradient-varying lithiophilic nucleation site on the negative electrode side, thereby achieving uniform control of the entire lithium-ion extraction-migration-deposition process.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a negative electrode-free lithium-ion battery and its preparation method. Background Technology

[0002] Electrodeless lithium-ion batteries, by completely eliminating the negative electrode active material, are considered a key technological path to achieve energy densities of over 400 Wh / kg. Their working principle is as follows: during charging, lithium ions are released from the positive electrode and directly deposited on the surface of the copper foil current collector to form a lithium metal layer; during discharging, the lithium metal layer is peeled off from the current collector and embedded into the positive electrode.

[0003] However, this system faces two major challenges: First, uneven lithium deposition on the negative electrode side. The smooth copper foil surface lacks lithiophilic sites, causing lithium ions to tend to accumulate and deposit at tips or defects, forming lithium dendrites. Lithium dendrite growth not only punctures the separator, causing short circuits, but also increases the area of ​​side reactions with the electrolyte, accelerating the irreversible consumption of active lithium. Second, the ion transport bottleneck under high areal loading on the positive electrode side. To achieve ultra-high energy density, the positive electrode must employ a high areal loading design (typically greater than 25 mg / cm²). In traditional wet-coating positive electrode sheets, the binder, polyvinylidene fluoride (PVDF), is a non-electrochemically active insulator randomly distributed in the interparticle gaps, blocking some ion transport channels. This results in high porosity within the electrode sheet, elongating the lithium ion migration path and causing concentration polarization. This polarization, in turn, exacerbates the uneven deposition on the negative electrode side.

[0004] While some studies have explored improving lithium deposition behavior by coating copper foil with lithiophilic layers (such as silver, gold, and zinc), they often overlook the impact of the cathode structure on the uniformity of lithium-ion "source supply." If the lithium-ion flux extracted from the cathode is inherently uneven, even a lithiophilic layer on the anode cannot completely eliminate the problem of uneven deposition. Therefore, optimizing the internal pore structure of high areal loading cathode sheets, reducing ion transport tortuosity, and alleviating concentration polarization, thereby simultaneously improving lithium deposition behavior on the anode, has become a key direction for overcoming the technological bottleneck of anode-less lithium-ion batteries. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a negative electrode-free lithium-ion battery and its preparation method.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a negative electrode-free lithium-ion battery, the method comprising: A high-nickel ternary active material, a conductive agent, and a binder are mixed and stirred to cause the binder to become fibrous, resulting in a mixed powder. The mixed powder is subjected to hot rolling treatment to obtain a self-supporting electrode film; The self-supporting electrode film is hot-pressed and composited with a carbon-coated aluminum foil current collector to obtain a positive electrode sheet. A negative electrode sheet with a lithiophilic modification layer is obtained by subjecting a copper foil current collector to lithiophilic treatment. The positive electrode, negative electrode, and separator are stacked into a cell, injected with a prepared electrolyte, vacuum-sealed and left to stand, to obtain the negative electrode-free lithium-ion battery.

[0007] Preferably, the mass ratio of the high-nickel ternary active material, the conductive agent, and the binder is [95-96.5]:[2-2.5]:[1.5-2.5].

[0008] Preferably, the adhesive is one or both of polytetrafluoroethylene and ultra-high molecular weight polyethylene.

[0009] Preferably, the mixing speed is 2100rpm-2200rpm, the temperature is 90℃-110℃, and the time is 10min-20min.

[0010] Preferably, the temperature of the hot roller pressing process is 80℃-110℃, and the pressure is 1T-5T.

[0011] Preferably, the hot-pressing composite treatment is performed at a temperature of 80℃-110℃ and a pressure of 5T-10T, and the areal loading of the positive electrode sheet is 20mg / cm². 2 -45mg / cm 2 The compacted density is 3.65 g / cm³. 3 .

[0012] Preferably, the lithiophilization treatment is achieved by magnetron sputtering, and the lithiophilic gradient modification layer includes a lithiophilic metal and a non-lithiophilic / weakly lithiophilic metal; the lithiophilic metal includes one or more of Ag, Au, Zn, and Mg; the non-lithiophilic / weakly lithiophilic metal includes one or more of Cu, Ni, and Ti.

[0013] More preferably, the mass fraction of the lithiophilic metal in the lithiophilic gradient modification layer is 0.001%-1% near the copper foil current collector and 1%-5% away from the copper foil current collector.

[0014] Preferably, the thickness of the carbon-coated aluminum foil current collector is 13μm-17μm, and the thickness of the copper foil current collector is 5μm-7μm.

[0015] In a second aspect, the present invention provides a negative electrode-free lithium-ion battery, wherein the negative electrode-free lithium-ion battery is prepared by any of the preparation methods described in the first aspect above.

[0016] This invention provides a method for fabricating a negative electrode-free lithium-ion battery. First, the fibrous binder network constructed using a dry electrode process not only acts as a binder but, more importantly, forms a low-torsion, interconnected vertical ion transport path within the positive electrode sheet. This significantly reduces ion transport resistance under high areal loading, ensuring that lithium ions can uniformly and rapidly reach the positive electrode surface and exit into the electrolyte, laying the foundation for ultra-high energy density. In other words, low-torsion ion transport is achieved on the positive electrode side. Second, by distributing lithiophilic elements in a gradient on the surface of the copper foil current collector, a gradual potential field is formed from a highly lithiophilic surface layer to a weakly lithiophilic bottom layer, simultaneously ensuring the uniformity of initial nucleation and the stability of subsequent growth. This achieves gradient-induced uniform deposition on the negative electrode side. Third, the synergistic effect of the positive and negative electrodes enables uniform control throughout the entire process. When the low-torsion positive electrode is used in conjunction with the gradient lithiophilic negative electrode, the uniform ion flow provided by the positive electrode and the gradient-induced nucleation of the negative electrode produce a synergistic effect. On the one hand, the uniform ion flow at the positive electrode ensures that the lithium ion flux reaching the negative electrode is spatially uniform; on the other hand, the gradient lithiophilic layer at the negative electrode ensures that these uniformly arriving lithium ions can nucleate and grow in a uniform manner.

[0017] In summary, this preparation method constructs low-torsion directional ion channels on the positive electrode side and simultaneously creates gradient-varying lithiophilic nucleation sites on the negative electrode side, thereby achieving uniform control of the entire lithium-ion process from extraction to migration to deposition. This end-to-end process control from source to deposition effectively solves the coupling failure problem caused by the mismatch between the positive and negative electrodes in traditional negative electrode-less lithium-ion batteries. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the preparation method of a negative electrode-free lithium-ion battery provided in an embodiment of the present invention. Figure 2 SEM image of the positive electrode sheet provided in the embodiment of the present invention; Figure 3 This is a cell cycle performance diagram provided in Embodiment 1 of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0021] This invention provides a method for preparing a negative electrode-free lithium-ion battery, the process of which is as follows: Figure 1 As shown, it includes the following steps: Step 110: Mix and stir the high-nickel ternary active material, conductive agent and binder to make the binder fibrous and obtain mixed powder; Specifically, the mass ratio of high-nickel ternary active material, conductive agent, and binder can be [95-96.5]:[2-2.5]:[1.5-2.5], preferably 96.5:2:1.5. The chemical formula of the high-nickel ternary active material (NCM) is LiNi. 1-x- y Co x Mn y The conductive agent can be, but is not limited to, conductive carbon black (Super P), Ketjen black, conductive graphite, and carbon nanotubes. The binder can be one or both of polytetrafluoroethylene (PTFE) and ultra-high molecular weight polyethylene (UHMWPE).

[0022] The mixing process can be carried out in a high-speed mixer at a speed of 2100-2200 rpm, a temperature of 90℃-110℃, and a time of 10-20 minutes. Preferably, the speed is 2000 rpm, the temperature is 100℃, and the time is 15 minutes.

[0023] During the mixing process, the binder can become fibrous, which provides the conditions for subsequent processing.

[0024] Step 120: The mixed powder is subjected to hot rolling treatment to obtain a self-supporting electrode film; Specifically, the hot rolling process can be carried out in a rolling mill at a temperature of 80℃-110℃ and a pressure of 1T-5T, with the preferred temperature being 100℃ and the pressure being 2T.

[0025] In this process, the fibrous binders interlock to form a three-dimensional network skeleton, improving mechanical strength. When the mixed powder passes through the roller gap, it is subjected to tensile force in the horizontal direction and compressive force in the vertical direction. Under the combined action of these two forces, the fibrous binder and high-nickel ternary active material particles rearrange, thus forming low-torsion, interconnected vertical ion transport channels in the thickness direction of the self-supporting electrode film. These vertical ion transport channels significantly reduce the tortuosity of lithium ion migration within the positive electrode, providing a rapid pathway for lithium ions to move from the positive electrode current collector towards the separator, ensuring uniform and rapid lithium ion extraction. Furthermore, the hot rolling process is a dry method for preparing the electrode structure, avoiding contact between the high-nickel ternary active material and water, thus improving interfacial stability. Moreover, the dry process eliminates the need for the toxic solvent N-methylpyrrolidone (NMP), making the preparation process environmentally friendly and pollution-free.

[0026] The thickness of the self-supporting electrode film can be 100μm-300μm.

[0027] Step 130: The self-supporting electrode film and the carbon-coated aluminum foil current collector are hot-pressed together to obtain the positive electrode sheet; Specifically, the hot-pressing composite treatment temperature can be 80℃-110℃, and the pressure can be 5T-10T, with the preferred temperature being 100℃ and the pressure being 6T. The single-sided surface loading of the positive electrode sheet is 20mg / cm². 2 -45mg / cm 2 The compacted density is 3.65 g / cm³. 3 The thickness of the carbon-coated aluminum foil current collector can be 13μm-17μm, preferably 15μm.

[0028] Generally speaking, the higher the areal load, the higher the mass energy density of the cell; the higher the compaction density, the higher the volume energy density of the cell. The areal load is also related to the roll gap range. In this application, the roll gap range is 0.1mm-0.4mm, but this is difficult to achieve with wet processing.

[0029] Step 140: The copper foil current collector is subjected to lithophilic treatment to obtain a negative electrode with a lithophilic gradient modification layer. Specifically, the lithiophilization process can be achieved using magnetron sputtering. The power of magnetron sputtering varies depending on the metal. The lithiophilic gradient modification layer includes a lithiophilic metal and a non-lithiophilic / weakly lithiophilic metal; the lithiophilic metal specifically includes one or more of Ag, Au, Zn, and Mg. The non-lithiophilic / weakly lithiophilic metal specifically includes one or more of Cu, Ni, and Ti. The thickness of the copper foil current collector is 6 μm-7 μm, preferably 6 μm. The thickness of the lithiophilic gradient modification layer can be 20 nm-25 nm.

[0030] The lithiophilic gradient modification layer exhibits a lithiophilic metal mass fraction of 0.001%-1% near the copper foil current collector and 1%-5% further away. This gradient distribution, occurring away from the copper foil current collector surface, creates a gradually changing lithiophilic potential field within the modification layer. Therefore, during the initial nucleation stage, lithium ions preferentially bind to the high-concentration lithiophilic sites on the surface, forming uniform nuclei. As deposition progresses, the weaker lithiophilic regions at the bottom act as buffers and confinement sites, preventing excessive local lithium metal growth and the formation of lithium dendrites. This gradient structure is more adaptable to the changing lithium behavior at different deposition stages than a single-concentration lithiophilic layer.

[0031] Step 150: Stack the positive electrode, negative electrode and separator into a cell, inject the prepared electrolyte, vacuum seal and let stand to obtain a negative electrode-free lithium-ion battery.

[0032] Specifically, the electrolyte preparation process for a negative electrode-free lithium-ion battery is as follows: In an argon glove box, 1 mol / L LiPF6 was dissolved in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), wherein the volume ratio of EC:EMC:DEC was 3:4:3, and the mixture was stirred until homogeneous.

[0033] Specifically, the diaphragm can be a 9μm thick ceramic-coated polyethylene diaphragm.

[0034] The electrolyte injection volume can be 2g / Ah, and the standing time can be 48 hours.

[0035] This invention provides a method for fabricating a negative electrode-free lithium-ion battery. First, the fibrous binder network constructed using a dry electrode process not only acts as a binder but, more importantly, forms a low-torsion, interconnected vertical ion transport path within the positive electrode sheet. This significantly reduces ion transport resistance under high areal loading, ensuring that lithium ions can uniformly and rapidly reach the positive electrode surface and exit into the electrolyte, laying the foundation for ultra-high energy density. In other words, low-torsion ion transport is achieved on the positive electrode side. Second, by distributing lithiophilic elements in a gradient on the surface of the copper foil current collector, a gradual potential field is formed from a highly lithiophilic surface layer to a weakly lithiophilic bottom layer, simultaneously ensuring the uniformity of initial nucleation and the stability of subsequent growth. This achieves gradient-induced uniform deposition on the negative electrode side. Third, the synergistic effect of the positive and negative electrodes enables uniform control throughout the entire process. When the low-torsion positive electrode is used in conjunction with the gradient lithiophilic negative electrode, the uniform ion flow provided by the positive electrode and the gradient-induced nucleation of the negative electrode produce a synergistic effect. On the one hand, the uniform ion flow at the positive electrode ensures that the lithium ion flux reaching the negative electrode is spatially uniform; on the other hand, the gradient lithiophilic layer at the negative electrode ensures that these uniformly arriving lithium ions can nucleate and grow in a uniform manner.

[0036] In summary, this preparation method constructs low-torsion directional ion channels on the positive electrode side and simultaneously creates gradient-varying lithiophilic nucleation sites on the negative electrode side, thereby achieving uniform control of the entire lithium-ion process from extraction to migration to deposition. This end-to-end process control from source to deposition effectively solves the coupling failure problem caused by the mismatch between the positive and negative electrodes in traditional negative electrode-less lithium-ion batteries.

[0037] To better understand the technical solution provided by the present invention, the following uses several specific examples to illustrate the specific process of preparing a negative electrode-free lithium-ion battery using the method provided in the above embodiments of the present invention, as well as the electrochemical characteristics of the prepared negative electrode-free lithium-ion battery.

[0038] Example 1 The first step involves adding high-nickel ternary active material (NCM), conductive carbon black, and polytetrafluoroethylene (PTFE) dry powder to a high-speed mixer at a mass ratio of 96.5:2:1.5 and mixing them to induce PTFE fibrosis, resulting in a mixed powder. The mixing speed was 2000 rpm, the temperature was 100℃, and the mixing time was 15 minutes.

[0039] The second step involves feeding the mixed powder into a roller press and subjecting it to continuous hot rolling at 100℃ and 2T pressure to obtain a self-supporting electrode film with a thickness of 184μm. The roller gap is 0.3mm.

[0040] The third step involves hot-pressing the self-supporting electrode film with a 15μm thick carbon-coated aluminum foil current collector at 100℃ and 6T to obtain the positive electrode sheet. The positive electrode sheet has an areal loading of 32mg / cm² and a compaction density of 3.65g / cm³.

[0041] In the fourth step, a dual-target magnetron sputtering system was used to co-sputter Ag and Cu targets onto one surface of a 6 μm thick copper foil current collector. During sputtering, the power of the Ag and Cu targets was independently adjusted to achieve a gradient change in Ag content. In the initial stage, the Ag target power was 20 W and the Cu target power was 200 W, resulting in an Ag content of approximately 0.03% in the deposited layer for 2 minutes. The Ag target power was increased to 80 W and the Cu target power was decreased to 140 W, gradually increasing the Ag content for 5 minutes. In the final stage, the Ag target power was 120 W and the Cu target power was 100 W, resulting in an Ag content of approximately 1% on the surface for 8 minutes. The total deposition time was 15 minutes, and the modified layer thickness was 25 nm. After deposition, a negative electrode sheet with Ag elemental gradient modification was obtained.

[0042] The fifth step involves stacking the positive electrode, negative electrode, and separator into a battery cell, injecting the prepared electrolyte, vacuum sealing, and allowing it to stand to obtain a negative electrode-free lithium-ion battery.

[0043] First, prepare the electrolyte: In an argon glove box, dissolve 1 mol / L LiPF6 in a mixed solvent of ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC), wherein the volume ratio of EC:EMC:DEC is 3:4:3, and stir until homogeneous.

[0044] Then, the battery is assembled and formed: using a 9μm thick ceramic-coated polyethylene separator, the above-prepared positive electrode, negative electrode and separator are stacked into a soft-pack cell, injected with 2g / Ah of prepared electrolyte, vacuum sealed and left to stand for 48 hours.

[0045] Test procedure: Charge and discharge tests were conducted in a 25℃ constant temperature chamber under the following conditions: voltage 2.8V-4.3V, charge and discharge rate 0.5C / 0.5C.

[0046] Electrode expansion rate test method: Using an in-situ expansion analyzer, a pressure of 20N is applied to the surface of the cell, and the expansion rate is measured in real time according to the cell cycle.

[0047] Example 2 The first to third steps are the same as in Example 1.

[0048] In the fourth step, a dual-target magnetron sputtering system was used to co-sputter Ag and Cu targets onto one surface of a 7 μm thick copper foil current collector. During sputtering, the power of the Ag and Cu targets was independently adjusted to achieve a gradient change in Ag content. In the initial stage, the Ag target power was 15 W and the Cu target power was 180 W, resulting in an Ag content of approximately 0.025% in the deposited layer for 1 min. The Ag target power was then increased to 70 W and the Cu target power decreased to 130 W, gradually increasing the Ag content for 1 min. In the final stage, the Ag target power was 120 W and the Cu target power was 100 W, resulting in an Ag content of approximately 1% on the surface for 8 min. The total deposition time was 10 min, and the modified layer thickness was 20 nm. After deposition, a negative electrode with Ag elemental gradient modification was obtained.

[0049] Step 5, same as in Example 1.

[0050] The testing process is the same as in Example 1.

[0051] Example 3 The first step involves adding high-nickel ternary active material (NCM), Ketjen black, and ultra-high molecular weight polyethylene (UHMWPE) dry powder to a high-speed mixer at a mass ratio of 95:2.5:2.5, and mixing them to induce fibrosis in the UHMWPE, resulting in a mixed powder. The mixing speed was 2100 rpm, the temperature was 90℃, and the mixing time was 20 minutes.

[0052] Steps two through five are the same as in Example 1.

[0053] The testing process is the same as in Example 1.

[0054] Example 4 The first step involves mixing high-nickel ternary active material (NCM), conductive graphite, and polytetrafluoroethylene (PTFE) dry powder in a high-speed mixer at a mass ratio of 96:2:2 to induce PTFE fibrosis and obtain a mixed powder. The mixing speed was 2200 rpm, the temperature was 110℃, and the mixing time was 10 minutes.

[0055] The second step involves feeding the mixed powder into a roller press and subjecting it to continuous hot rolling at 80°C and 10T to obtain a self-supporting electrode film with a thickness of 100μm. The roller gap is 0.1mm.

[0056] The third step involves hot-pressing the self-supporting electrode film with a 13μm thick carbon-coated aluminum foil current collector at 80℃ and 5T to obtain the positive electrode sheet. The positive electrode sheet has an areal loading of 20mg / cm² and a compaction density of 3.65g / cm³.

[0057] In the fourth step, a dual-target magnetron sputtering system was used to co-sputter Au and Ti targets onto one surface of a 6 μm thick copper foil current collector. During sputtering, the Au content was varied by independently controlling the power of the Au and Ti targets. Initially, the Au target power was 5 W and the Ti target power was 150 W, resulting in an Au content of approximately 0.001% in the deposited layer for 2 minutes. The Au target power was then increased to 80 W and the Ti target power decreased to 100 W, gradually increasing the Au content for 3 minutes. Finally, the Au target power was 120 W and the Ti target power was 60 W, resulting in a surface Au content of approximately 5% for 6 minutes. The total deposition time was 11 minutes, and the modified layer thickness was 22 nm. After deposition, a negative electrode with Au elemental gradient modification was obtained.

[0058] Step 5 is the same as in Example 1.

[0059] The testing process is the same as in Example 1.

[0060] Example 5 The first step involves adding high-nickel ternary active material (NCM), carbon nanotubes, and ultra-high molecular weight polyethylene (UHMWPE) dry powder to a high-speed mixer at a mass ratio of 95.5:2.5:2, and mixing them to induce fibrosis in the UHMWPE, resulting in a mixed powder. The mixing speed was 2150 rpm, the temperature was 105℃, and the mixing time was 18 minutes.

[0061] The second step involves feeding the mixed powder into a roller press and subjecting it to continuous hot rolling at a temperature of 110℃ and a pressure of 1T to obtain a self-supporting electrode film with a thickness of 300μm. The roller gap is 0.4mm.

[0062] The third step involves hot-pressing the self-supporting electrode film with a 17μm thick carbon-coated aluminum foil current collector at 110℃ and 5T to obtain the positive electrode sheet. The positive electrode sheet has an areal loading of 40mg / cm² and a compaction density of 3.65g / cm³.

[0063] In the fourth step, a dual-target magnetron sputtering system was used to co-sputter Mg and Ni targets onto one surface of a 7 μm thick copper foil current collector. During sputtering, the power of the Mg and Ni targets was independently adjusted to achieve a gradient change in Mg content. In the initial stage, the Mg target power was 25 W and the Ni target power was 90 W, with a Mg content of approximately 0.03% in the deposited layer, lasting for 3 min. The Mg target power was increased to 75 W and the Ni target power was decreased to 80 W, gradually increasing the Mg content, lasting for 3 min. In the final stage, the Mg target power was 150 W and the Ni target power was 75 W, with a surface Mg content of approximately 1%, lasting for 6 min. The total deposition time was 12 min, and the modified layer thickness was 23 nm. After deposition, a negative electrode sheet modified with a gradient change in Mg element was obtained.

[0064] Step 5 is the same as in Example 1.

[0065] The testing process is the same as in Example 1.

[0066] Comparative Example 1 The first step involves mixing NCM, conductive carbon black, and PVDF in a mass ratio of 96.5:2:1.5 with NMP to form a slurry. This slurry is then coated onto aluminum foil and dried in a 5-meter continuous oven at temperatures of 45℃, 50℃, and 55℃ at a speed of 2m / s. The rollers are then pressed with a gap of 0.1mm and a pressure of 150T to obtain a positive electrode sheet with an surface loading of 30mg / cm² and a compaction density of 3.5g / cm³.

[0067] The second step involves stacking the positive electrode, negative electrode (unmodified copper foil current collector), and separator into a battery cell, injecting the prepared electrolyte, vacuum sealing, and allowing it to stand to obtain a negative electrode-free lithium-ion battery.

[0068] First, prepare the electrolyte: In an argon glove box, dissolve 1 mol / L LiPF6 in a mixed solvent of ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC), wherein the volume ratio of EC:EMC:DEC is 3:4:3, and stir until homogeneous.

[0069] Then, the battery is assembled and formed: using a 9μm thick ceramic-coated polyethylene separator, the above-prepared positive electrode, negative electrode and separator are stacked into a soft-pack cell, injected with 2g / Ah of prepared electrolyte, vacuum sealed and left to stand for 48 hours.

[0070] The testing process is the same as in Example 1.

[0071] Comparative Example 2 The first to third steps are the same as in Example 1.

[0072] The fourth step involves using a magnetron sputtering system to deposit Ag on one surface of a 6 μm thick copper foil current collector. After deposition, a negative electrode with an Ag coating is obtained. The Ag content is 5%, and the coating thickness is 25 nm.

[0073] Step 5, same as in Example 1.

[0074] The testing process is the same as in Example 1.

[0075] Comparative Example 3 The first step involves mixing NCM, conductive carbon black, and PVDF in a mass ratio of 96.5:2:1.5 with NMP to form a slurry, which is then coated onto aluminum foil. After drying and rolling, a positive electrode sheet with an areal loading of 30 mg / cm² and a compaction density of 3.5 g / cm³ is obtained.

[0076] The second step involved co-sputtering an Ag target and a Cu target onto a single surface of a 6 μm thick copper foil current collector using a dual-target magnetron sputtering system. During sputtering, the power of the Ag and Cu targets was independently adjusted to achieve a gradient change in Ag content. Initially, the Ag target power was 20 W and the Cu target power was 200 W, resulting in an Ag content of approximately 0.03% in the deposited layer for 2 minutes. The Ag target power was then increased to 80 W and the Cu target power decreased to 140 W, gradually increasing the Ag content for 5 minutes. Finally, the Ag target power was 120 W and the Cu target power was 100 W, resulting in a surface Ag content of approximately 1% for 8 minutes. The total deposition time was 15 minutes, and the modified layer thickness was 25 nm. After deposition, a negative electrode plate modified with a gradient change in Ag elemental composition was obtained.

[0077] The third step involves stacking the positive electrode, negative electrode, and separator into a battery cell, injecting the prepared electrolyte, vacuum sealing, and allowing it to stand to obtain a negative electrode-free lithium-ion battery.

[0078] First, prepare the electrolyte: In an argon glove box, dissolve 1 mol / L LiPF6 in a mixed solvent of ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC), wherein the volume ratio of EC:EMC:DEC is 3:4:3, and stir until homogeneous.

[0079] Then, the battery is assembled and formed: using a 9μm thick ceramic-coated polyethylene separator, the above-prepared positive electrode, negative electrode and separator are stacked into a soft-pack cell, injected with 2g / Ah of prepared electrolyte, vacuum sealed and left to stand for 48 hours.

[0080] The testing process is the same as in Example 1.

[0081] Table 1 summarizes the test data of Examples 1-5 and Comparative Examples 1-3 of the present invention.

[0082] Table 1 As shown in Table 1, the lithium-ion batteries in Examples 1-5, which adopt the structure design of the present invention, have an initial energy density of over 420Wh / kg, a capacity retention rate of over 81% after 20 cycles, and an electrode expansion rate of less than 10%. The capacity retention rate and electrode expansion rate are far superior to those of Comparative Examples 1-3.

[0083] Combination Figure 3 As shown, Comparative Example 1, using a wet-process positive electrode and smooth copper foil, exhibited a capacity retention of only 48% after 20 cycles, with a short circuit occurring after 15 cycles and an electrode expansion rate of 45%. Comparative Example 2, using only a dry-process positive electrode and a uniformly lithiophilic layer for the negative electrode, achieved a capacity retention of approximately 81% after 20 cycles, with an electrode expansion rate of 19%. Comparative Example 3, using only a negative electrode with a lithiophilic gradient modification layer and a wet-process positive electrode, achieved a capacity retention of only 63% after 20 cycles and experienced a micro-short circuit. These data fully demonstrate the significant advancements in the positive and negative electrode synergistic structure design of this invention.

[0084] Both Example 1 and Comparative Example 3 employed gradient lithiophilic anodes, but the cycle capacity retention of the dry cathode (low tortuosity) in Example 1 (82%) was significantly higher than that of the wet cathode (63%) in Comparative Example 3. This indicates that even if the anode has excellent lithiophilic induction ability, if the ion transport channels of the cathode are obstructed (high tortuosity), it will lead to uneven lithium ion extraction, thereby affecting the uniformity of anode deposition.

[0085] Both Example 1 and Comparative Example 2 used dry cathodes, but the gradient lithiophilic anode of Example 1 exhibited a better cycle capacity retention (82%) and expansion rate (8%) than the uniform lithiophilic anode of Comparative Example 2 (81% cycle capacity retention and 19% expansion rate). This indicates that the lithiophilic gradient modification layer (gradient lithiophilic layer) is more adaptable to different stages of lithium deposition behavior than a uniform coating, providing a longer-lasting regulatory effect. Most importantly, the overall performance of Example 1 (dry cathode + gradient lithiophilic layer) was significantly better than the other comparative examples, demonstrating a synergistic enhancement effect between the low-torsion channel of the cathode and the gradient lithiophilic layer of the anode. Together, they achieved uniformity throughout the lithium-ion deposition process, effectively suppressing dendrite growth and extending cycle life.

[0086] In summary, this invention effectively solves the ion transport bottleneck and uneven lithium deposition problems in high areal loading lithium batteries by constructing low-torsivity ion channels on the positive electrode side and gradient lithiophilic nucleation sites on the negative electrode side through structural innovation. This structural design enables the battery to achieve an ultra-high energy density of over 420 Wh / kg while maintaining excellent cycle stability, demonstrating significant progress and industrial applicability.

[0087] like Figure 2 As shown, the dry-processed electrode exhibits a low-torsion, interconnected, vertical ion transport path, ensuring that lithium ions can uniformly and rapidly reach the positive electrode surface and exit into the electrolyte, laying the foundation for ultra-high energy density in the battery. In other words, low-torsion ion transport is achieved on the positive electrode side.

[0088] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a negative electrode-free lithium-ion battery, characterized in that, The preparation method includes: A high-nickel ternary active material, a conductive agent, and a binder are mixed and stirred to cause the binder to become fibrous, resulting in a mixed powder. The mixed powder is subjected to hot rolling treatment to obtain a self-supporting electrode film; The self-supporting electrode film is hot-pressed and composited with a carbon-coated aluminum foil current collector to obtain a positive electrode sheet. A negative electrode sheet with a lithiophilic modification layer is obtained by subjecting a copper foil current collector to lithiophilic treatment. The positive electrode, negative electrode, and separator are stacked into a cell, injected with a prepared electrolyte, vacuum-sealed and left to stand, to obtain the negative electrode-free lithium-ion battery.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the high-nickel ternary active material, conductive agent, and binder is [95-96.5]:[2-2.5]:[1.5-2.5].

3. The preparation method according to claim 1, characterized in that, The adhesive is one or both of polytetrafluoroethylene and ultra-high molecular weight polyethylene.

4. The preparation method according to claim 1, characterized in that, The mixing and stirring speed is 2100rpm-2200rpm, the temperature is 90℃-110℃, and the time is 10min-20min.

5. The preparation method according to claim 1, characterized in that, The temperature of the hot roller pressing process is 80℃-110℃, and the pressure is 1T-5T.

6. The preparation method according to claim 1, characterized in that, The hot-pressing composite treatment is carried out at a temperature of 80℃-110℃ and a pressure of 5T-10T. The single-sided surface loading of the positive electrode sheet is 20mg / cm². 2 -45mg / cm 2 The compacted density is 3.65 g / cm³. 3 .

7. The preparation method according to claim 1, characterized in that, The lithiophilization treatment is achieved by magnetron sputtering, and the lithiophilic gradient modification layer includes a lithiophilic metal and a non-lithiophilic / weakly lithiophilic metal; the lithiophilic metal includes one or more of Ag, Au, Zn, and Mg; the non-lithiophilic / weakly lithiophilic metal includes one or more of Cu, Ni, and Ti.

8. The preparation method according to claim 7, characterized in that, The lithiophilic gradient modification layer has a lithiophilic metal mass fraction of 0.001%-1% near the copper foil current collector and a lithiophilic metal mass fraction of 1%-5% far from the copper foil current collector.

9. The preparation method according to claim 1, characterized in that, The thickness of the carbon-coated aluminum foil current collector is 13μm-17μm, and the thickness of the copper foil current collector is 5μm-7μm.

10. A negative electrode-free lithium-ion battery, characterized in that, The negative electrode-free lithium-ion battery is prepared by any one of the preparation methods described in claims 1-9.

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