A lithium metal anode pre-stripping method based on chromium oxide coated multi-dimensional electrode, lithium metal battery and electrical equipment

Abstract

The application provides a lithium metal negative electrode pre-stripping method based on a chromium oxide coated multi-dimensional electrode, a lithium metal battery and an electrical device, and relates to the field of lithium metal battery preparation. The method comprises the following steps: coating Cr8O 21 an active material layer, Cr8O 21 The active material is in a lithium-poor oxidation state, and Cr8O 21 a coated multi-dimensional positive electrode; coating Cr8O 21 The coated multi-dimensional positive electrode, the lithium metal negative electrode, the electrolyte and the separator are assembled to obtain a secondary lithium metal full battery; and the secondary lithium metal full battery is subjected to a first small-current discharge activation treatment, so that uniform distribution of pits and / or active sites are generated on the surface of the lithium metal negative electrode. The method can continuously induce uniform deposition of lithium ions in the long-term cycle of the lithium metal negative electrode, effectively inhibits the generation of lithium dendrites and dead lithium, and thus significantly improves the cycle life and safety of the secondary lithium metal battery.

Description

Technical Field

[0001] This application relates to the field of lithium metal battery preparation, and in particular to a method for pre-stripping lithium metal anodes based on chromium oxide coated multidimensional electrodes, lithium metal batteries, and electrical devices. Background Technology

[0002] Lithium metal, due to its high theoretical specific capacity and low electrode potential, is considered an important anode material for next-generation high-energy-density rechargeable batteries. However, during charge-discharge cycles, non-uniform deposition of lithium ions easily occurs on the surface of lithium metal anodes, leading to the formation of lithium dendrites. The growth of lithium dendrites can not only puncture the battery separator and cause a short circuit risk, but also cause irreversible consumption of lithium ions, forming "dead lithium," thereby reducing the battery's cycle life and coulombic efficiency, thus restricting the commercial application of lithium metal rechargeable batteries.

[0003] To suppress lithium dendrite growth, existing technologies mainly focus on anode alloying, introducing carbon-based or metal-based frameworks to the surface, constructing artificial solid electrolyte interface films, optimizing electrolyte composition, and modifying separators. Pre-modifying the lithium metal anode to create uniform active deposition sites on its surface is one effective way to induce uniform lithium-ion deposition and suppress dendrite growth. However, most existing pre-modification methods require separate treatment of the lithium metal anode before battery assembly (e.g., chemical etching, physical polishing), which is cumbersome, costly, and the constructed active sites are prone to failure during subsequent cycles, making it difficult to achieve long-term stable dendrite suppression. Therefore, how to perform in-situ surface pretreatment of the lithium metal anode through a simple electrochemical process and effectively induce uniform lithium-ion deposition during battery cycling is a key technical problem to be solved to improve the cycle life of rechargeable lithium metal batteries. Summary of the Invention

[0004] The purpose of this application is to provide a method for pre-stripping lithium metal anodes based on chromium oxide coated multidimensional electrodes, lithium metal batteries, and electrical devices to solve the above-mentioned problems.

[0005] To achieve the above objectives, this application adopts the following technical solution: This application provides a method for pre-stripping lithium metal anodes based on chromium oxide-coated multidimensional electrodes, including: Cr8O is coated on the surface of the positive electrode substrate. 21 Active material layer, the Cr8O 21 The active material is in a lithium-poor oxidation state, and Cr8O is prepared. 21 Coated multidimensional positive electrode; Cr8O 21 The coated multidimensional positive electrode, lithium metal negative electrode, electrolyte and separator are assembled to obtain a secondary lithium metal full cell; The secondary lithium metal full cell is subjected to a first low-current discharge activation treatment to generate uniformly distributed pits and / or active sites on the surface of the lithium metal anode.

[0006] Optionally, the material of the positive electrode substrate includes one or more of lithium manganese oxide, lithium iron phosphate, lithium cobalt oxide, nickel-cobalt-manganese ternary materials, and nickel-cobalt-aluminum ternary materials.

[0007] Optionally, the lithium metal anode includes one of lithium foil, lithium alloy foil, or lithium-based composite anode.

[0008] Optionally, the electrolyte includes one of carbonate electrolytes, ether electrolytes, or ionic liquid electrolytes.

[0009] Optionally, the diaphragm comprises one or more of polypropylene, polyimide, polybenzimidazole, cellulose nonwoven fabric, polyvinylidene fluoride porous membrane, and polyethylene.

[0010] Optionally, the Cr8O 21 The active material was prepared by a high-temperature solid-state method, using CrO3 as a precursor and pyrolyzing it at 270℃-290℃.

[0011] Optionally, the Cr8O 21 The particle size of the active material is 50-10000 nm.

[0012] Optionally, the Cr8O 21 The coating thickness of the active material is 0.5-20 μm, and the coating amount is 5%-20% of the mass of the positive electrode substrate material.

[0013] Optionally, the multidimensional positive electrode has a hierarchical porous structure, wherein the macropores formed by the accumulation of positive electrode substrate material particles have a pore size of 50-500 nm, and the Cr8O 21 The mesopores formed by the coating have a diameter of 10-50 nm.

[0014] Optionally, the thickness of the lithium metal anode is 10-500 μm.

[0015] Optionally, the electrolyte further includes lithium salt; the amount of lithium salt added is 0.1%-5% of the total mass of the electrolyte.

[0016] The lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(oxalate-borate), lithium difluorooxalate-borate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide.

[0017] Optionally, the conditions for the initial low-current discharge activation are: cell ambient temperature 25-60℃, cell restraint pressure 20-200kPa, discharge current density 0.005-0.2C, discharge cutoff voltage 1.5-2.5V, discharge mode is constant current discharge, and discharge time is 1-5 h.

[0018] This application also provides a lithium metal battery, the preparation method of which includes the method based on Cr8O. 21 A method for pre-stripping lithium metal anodes coated with multidimensional electrodes.

[0019] This application also provides an electrical device, including the lithium metal battery.

[0020] Compared with the prior art, the beneficial effects of this application include: The application provides the use of Cr8O 21 The lithium-poor oxidation state characteristics of Cr8O during the first low-current discharge process... 21 This method consumes lithium ions, forcing the lithium metal anode to undergo controllable and uniform pre-stripping, generating pits / active sites in situ. It eliminates the need for separate pretreatment of the lithium metal anode before battery assembly, such as chemical etching or physical polishing, simplifying the process and reducing costs. Simultaneously, the in-situ generated active sites bond firmly to the anode, resisting detachment and continuously inducing uniform lithium ion deposition during long-term cycling. This effectively suppresses the formation of lithium dendrites and dead lithium, significantly improving the cycle life and safety of rechargeable lithium metal batteries.

[0021] The battery product provided in this application has uniform and stable pits / active sites formed in situ on the surface of the internal lithium metal anode, requiring no additional treatment from the user. During actual charge-discharge cycles, these sites continuously induce uniform lithium-ion deposition, significantly inhibiting the growth of lithium dendrites and dead lithium, thereby endowing the battery with high coulombic efficiency, long cycle life, and good safety performance, overcoming the bottleneck of poor cycle stability in existing lithium metal batteries.

[0022] Applying the aforementioned lithium metal batteries, which possess long cycle life and high safety, to electrical equipment (such as electric vehicles, energy storage systems, and portable electronic products) can effectively extend the equipment's battery life and service life, reduce maintenance costs and safety risks caused by battery failure, and improve the overall reliability and market competitiveness of the equipment. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0024] Figure 1Cr8O prepared for the example 21 A physical image of the coated multidimensional positive electrode; Figure 2 This is a comparison chart of the battery cycle life of Comparative Example 1 and Example 2. Detailed Implementation

[0025] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0026] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0027] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0028] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0029] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0030] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0031] To better explain the technical solution provided in this application, the technical solution provided in this application will be described in general before the specific implementation.

[0032] This application provides a method for pre-stripping lithium metal anodes based on chromium oxide-coated multidimensional electrodes, including: Cr8O is coated on the surface of the positive electrode substrate. 21 Active material layer, the Cr8O 21 The active material is in a lithium-poor oxidation state, and Cr8O is prepared. 21 Coated multidimensional positive electrode; Cr8O 21 The coated multidimensional positive electrode, lithium metal negative electrode, electrolyte and separator are assembled to obtain a secondary lithium metal full cell; The secondary lithium metal full cell is subjected to a first low-current discharge activation treatment to generate uniformly distributed pits and / or active sites on the surface of the lithium metal anode. Common cathode materials for existing rechargeable lithium metal batteries (such as LiCoO2 and LiFePO4) are all in a lithium-rich reduced state, containing a large number of lithium ions. During the first discharge after battery assembly, they primarily undergo their own delithiation reaction, failing to consume the lithium ions in the battery system to promote pre-stripping of the lithium metal anode. In contrast, Cr8O... 21 In its lithium-poor oxidation state, its crystal structure does not contain lithium ions that can be intercalated or deintercalated. During the first discharge, a lithium intercalation reaction occurs, consuming lithium ions in the battery system. This forces the lithium metal anode to undergo an oxidation reaction (i.e., pre-stripping), generating uniform pits / active sites, increasing the specific surface area of ​​the lithium metal anode surface, and thus improving contact with the electrolyte, providing a foundation for subsequent uniform lithium ion deposition. Meanwhile, Cr8O... 21 It exhibits good electrochemical reversibility, contributes to the capacity of secondary batteries, does not negatively affect the electrochemical performance of batteries, and possesses excellent electrochemical performance.

[0033] This solves the technical challenge of pre-stripping lithium metal anodes using existing common cathode materials: by coating the cathode material surface with lithium-depleted Cr8O. 21 The active material spontaneously consumes lithium ions through a reduction reaction during its first discharge, achieving uniform pre-stripping of the lithium metal anode. This eliminates the need for separate pre-modification of the lithium metal anode, simplifying the battery manufacturing process and reducing production costs.

[0034] Effectively suppresses lithium dendrite and dead lithium generation: After the initial low-current discharge activation, uniformly distributed pits / active sites are generated on the surface of the lithium metal anode, which can significantly reduce the local current density and induce uniform lithium ion deposition during subsequent cycles. This fundamentally suppresses the growth of lithium dendrites and the generation of dead lithium, avoids the risk of battery short circuit, and improves battery safety.

[0035] Significantly improves battery cycle life: Cr8O 21 The coated multidimensional electrode not only enables lithium anode pre-stripping, but its multidimensional porous structure also improves ion transport efficiency, while Cr8O 21 It possesses good electrochemical reversibility and can contribute to battery capacity, synergistically improving the cycle stability and coulombic efficiency of secondary lithium metal batteries.

[0036] In one optional embodiment, the material of the positive electrode substrate includes one or more of lithium manganese oxide, lithium iron phosphate, lithium cobalt oxide, nickel-cobalt-manganese ternary materials, and nickel-cobalt-aluminum ternary materials.

[0037] In one optional embodiment, the lithium metal anode comprises one of lithium foil, lithium alloy foil, or lithium-based composite anode.

[0038] In one optional embodiment, the electrolyte includes one of carbonate electrolytes, ether electrolytes, or ionic liquid electrolytes.

[0039] In one alternative embodiment, the diaphragm comprises one or more of polypropylene, polyimide, polybenzimidazole, cellulose nonwoven fabric, polyvinylidene fluoride porous membrane, and polyethylene.

[0040] The aforementioned materials are all common and mature secondary lithium metal battery components in this field, ensuring the broad applicability and feasibility of this technical solution. By combining these conventional materials, application requirements such as different energy densities, rate performance, and operating temperatures can be met, while not affecting the performance of Cr8O. 21 The core effect of the coating and pre-peeling methods is that they can be directly applied to existing battery production lines.

[0041] In an optional implementation, the Cr8O 21 The active material was prepared by a high-temperature solid-state method, using CrO3 as a precursor and pyrolyzing it at 270℃-290℃.

[0042] This temperature range is for the pyrolysis of CrO3 to produce Cr8O. 21 The optimal process window for obtaining Cr8O at this temperature 21 It exhibits the highest crystallinity and purest phase, avoiding incomplete precursor reactions (resulting in residual CrO3) due to excessively low temperatures or the formation of impurities such as Cr2O5 and Cr2O3 due to excessively high temperatures. High crystallinity and high purity Cr8O21 It has stable electrochemical activity and can provide precise lithium-ion consumption capability during the first discharge, thereby ensuring the uniformity and controllability of pre-stripping on the lithium metal anode surface.

[0043] In an optional implementation, the Cr8O 21 The particle size of the active material is 50-500 nm.

[0044] 50-500nm nanoscale Cr8O 21 The particles have a high specific surface area and short ion diffusion paths, which are beneficial to improving the reaction kinetics during the first discharge.

[0045] Optional, Cr8O 21 The particle size of the active material can be 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, or any value between 50 and 10000 nm.

[0046] In an optional implementation, the Cr8O 21 The coating thickness of the active material is 0.5-5μm, and the coating amount is 5%-20% of the mass of the positive electrode substrate material.

[0047] A coating thickness of 0.5-20 μm provides sufficient reaction capacity to complete pre-stripping without excessively increasing electrode internal resistance or sacrificing positive electrode energy density. Controlling the coating amount between 5% and 20% ensures a moderate amount of lithium ions consumed during the first discharge, resulting in a suitable density of pits / active sites on the lithium metal anode surface, avoiding both excessive damage to the anode and insufficient pre-stripping.

[0048] Optional, Cr8O 21 The coating thickness of the active material can be 0.5μm, 5μm, 10μm, 15μm, 20μm, or any value between 0.5 and 20μm; the coating amount can be 5%, 10%, 15%, 20% of the mass of the positive electrode substrate material, or any value between 5 and 20%.

[0049] In one optional embodiment, the multidimensional positive electrode has a hierarchical porous structure, wherein the macropores formed by the accumulation of positive electrode substrate material particles have a pore size of 50-500 nm, and are composed of Cr8O 21 The mesopores formed by the coating have a diameter of 10-50 nm.

[0050] Macroporous structures serve as the main transport channels for lithium ions, while mesoporous structures promote the transport of lithium ions to Cr8O. 21 Rapid diffusion of active sites. The hierarchical porous structure significantly increases the specific surface area and reactivity of the electrode, enabling lithium ions to react with Cr8O during the first discharge. 21The coating ensures full contact, achieving large-area, uniform pre-stripping of the lithium metal anode surface and preventing localized over- or under-reaction. Simultaneously, this multi-dimensional structure facilitates rapid lithium-ion transport during subsequent normal charging and discharging, reducing polarization and further improving battery rate performance.

[0051] Optionally, the macropore size formed by the accumulation of positive electrode substrate material particles can be 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, or any value between 50-500nm; Cr8O 21 The mesopore size formed by the coating can be 10nm, 20nm, 30nm, 40nm, 50nm, or any value between 10-50nm.

[0052] In one optional embodiment, the thickness of the lithium metal anode is 10-500 μm.

[0053] Optionally, the thickness of the lithium metal anode can be 10μm, 100μm, 200μm, 300μm, 400μm, 500μm, or any value between 10 and 500μm.

[0054] In an optional embodiment, the electrolyte further includes a lithium salt; the amount of lithium salt added is 0.1%-5% of the total mass of the electrolyte.

[0055] Optionally, the amount of lithium salt added can be 0.1%, 1%, 2%, 3%, 4%, 5% of the total mass of the electrolyte, or any value between 0.1% and 5%.

[0056] The lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(oxalate-borate), lithium difluorooxalate-borate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide.

[0057] In one optional implementation, the conditions for the initial low-current discharge activation are: cell ambient temperature 25-60℃, cell restraint pressure 20-200kPa, discharge current density 0.005-0.2C, discharge cutoff voltage 1.5-2.5V, discharge mode is constant current discharge, and discharge time is 1-5 h.

[0058] The low current (0.005-0.2 C) and long time (1-5 h) ensure slow dynamic control of the discharge process, so that the lithium metal on the surface of the lithium metal anode is uniformly and slowly stripped away, generating uniformly distributed pits / active sites with controllable size, avoiding the formation of defects caused by excessive local stripping due to high current.

[0059] A cutoff voltage of 1.5-2.5V ensures Cr8O 21It is fully reduced (its reduction potential range is within this range), completely consuming the lithium ions required by the design, while avoiding over-discharge and damage to the positive electrode structure.

[0060] An ambient temperature of 25-60℃ and a confinement pressure of 20-200 kPa simulate the actual battery operating conditions, ensuring the stability and repeatability of the electrochemical reaction.

[0061] The synergistic effect of the above conditions enabled high-quality in-situ pre-modification of the lithium metal anode surface.

[0062] This application also provides a lithium metal battery, the preparation method of which includes the method described above based on Cr8O. 21 A method for pre-stripping lithium metal anodes coated with multidimensional electrodes.

[0063] This application also provides a lithium metal battery and an electrical device including the lithium metal battery.

[0064] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0065] Example 1 This embodiment provides a method for pre-stripping lithium metal anodes based on chromium oxide-coated multidimensional electrodes. The specific process is as follows: Using CrO3 as a precursor, Cr8O was obtained by high-temperature solid-state method, pyrolysis at 290℃ for 2 h, followed by cooling and grinding to a particle size of 200-300 nm. 21 Active materials.

[0066] With 9-series NCM (LiNi 0.9 Co 0.05 Mn 0.05 O2) is used as the positive electrode material, binder (PVDF), and conductive agent (Super P) mixed in a mass ratio of 97.5:1.2:1.3. NMP solvent is added, and the mixture is stirred evenly to form a coating slurry. The slurry is then coated onto the aluminum foil current collector using a coating machine, with a single-sided loading of 20 mg / cm². 2 Double-sided coating and drying; Cr8O 21 Active material, binder (PVDF), and conductive agent (Super P) are mixed in a mass ratio of 96:2:2, NMP solvent is added, and the mixture is stirred until homogeneous to form a coating slurry. This slurry is then coated onto the surface of a 9-series NCM positive electrode sheet, with a coating amount of 5% of the 9-series NCM positive electrode load. After baking, the electrode sheet is rolled to obtain Cr8O.21 Coated multidimensional positive electrode, such as Figure 1 As shown.

[0067] The obtained multidimensional positive electrode sheet is cut into pieces 65mm wide and 95mm long, with tabs (15mm wide and 10mm long) reserved. For the negative electrode, 100um lithium metal foil is cut into pieces 97mm long and 67mm wide. Copper metal foil tabs 10mm long and 15mm wide are attached to the lithium metal foil and rolled together to obtain the negative electrode sheet.

[0068] Using two multidimensional positive electrode sheets, three lithium foil negative electrodes with a thickness of 100 μm, and a polypropylene separator with a thickness of 16 μm, the electrodes are stacked in a Z-shape. After stacking, positive and negative electrode tabs are welded, and the batteries are packaged with an aluminum-plastic film. The electrolyte is a 1 mol / L LiPF6 EC / DMC / EMC solution (volume ratio 1:1:1), with an injection volume of 2.5 g, to obtain a secondary lithium metal pouch battery with a capacity of 1 Ah.

[0069] The assembled pouch battery was left to stand at room temperature for 2 hours, then placed in a constant temperature environment of 25°C. A constraint force of 300 kPa was applied to both sides of the cell, and it was discharged at a constant current density of 0.05 C with a discharge cutoff voltage of 2.0 V to complete the first pre-discharge activation, which generated uniformly distributed pits / active sites on the surface of the lithium metal anode.

[0070] After activation, a charge-discharge cycle test was conducted using a 0.2C charge-0.5C discharge cycle, with a charge-discharge cutoff voltage of 2.5-4.3 V.

[0071] Example 2 This embodiment provides a pre-stripping method for lithium metal anodes based on chromium oxide-coated multidimensional electrodes. The only difference from Embodiment 1 is the preparation of Cr8O. 21 In the coating of the multidimensional positive electrode, Cr8O 21 The coating load was adjusted to 10% of the 9-series NCM load.

[0072] Example 3 This embodiment provides a pre-stripping method for lithium metal anodes based on chromium oxide-coated multidimensional electrodes. The only difference from Embodiment 1 is the preparation of Cr8O. 21 In the coating of the multidimensional positive electrode, Cr8O 21 The coating load was adjusted to 15% of the 9-series NCM load.

[0073] Comparative Example 1 This comparative example provides a secondary lithium metal pouch battery. The secondary lithium metal pouch battery is assembled using the same method as in Example 1, the difference being that the positive electrode uses Cr8O-free material. 21 Coated 9-series NCM (LiNi)0.9 Co 0.05 Mn 0.05 The battery was tested using an O2 electrode, without initial low-current discharge activation, and directly underwent charge-discharge cycle testing with a 0.2C charge-0.5C discharge cycle. A comparison of the cycle life with that of Example 2 is shown in the figure below. Figure 2 As shown.

[0074] Comparative Example 2 This comparative example provides a secondary lithium metal pouch battery. The only difference from Example 1 is that it does not undergo an initial low-current discharge activation. Instead, it is directly tested for charge-discharge cycles using a 0.2C charge-0.5C discharge cycle, with a charge-discharge cutoff voltage of 2.5-4.3 V. All other steps and parameters remain unchanged.

[0075] Comparative Example 3 This comparative example provides a secondary lithium metal pouch battery, which differs from Example 1 only in that the positive electrode uses Cr8O-free material. 21 Coated 9-series NCM (LiNi) 0.9 Co 0.05 Mn 0.05 O2 electrode. Other steps and parameters remain unchanged.

[0076] Comparative Example 4 This comparative example provides a secondary lithium metal pouch battery, differing from Example 1 only in the preparation of Cr8O. 21 A dense coating is used during the coating process, and mesopores are eliminated through high roller pressure. Other steps and parameters remain unchanged.

[0077] Comparative Example 5 This comparative example provides a secondary lithium metal pouch battery, which differs from Example 1 only in that: CrO3 is used as the precursor, and the pyrolysis temperature using the high-temperature solid-state method is 250°C. All other steps and parameters remain unchanged.

[0078] Comparative Example 6 This comparative example provides a secondary lithium metal pouch battery, which differs from Example 1 only in that: CrO3 is used as a precursor, and the pyrolysis temperature using the high-temperature solid-state method is 310°C. All other steps and parameters remain unchanged.

[0079] The performance tests of the batteries prepared in the examples and comparative examples are shown in Table 1.

[0080] Table 1. Performance of the batteries prepared in the examples and comparative examples.

[0081] As can be seen from the test data in the table above, in Examples 1, 2, and 3, with the increase of Cr8O 21With an increased coating quality ratio, the cell's internal resistance tends to decrease during the initial anti-electrolysis process. This is because the lithium metal anode undergoes varying degrees of electrochemical stripping. This indicates that during the pre-stripping process of the lithium metal anode, the electrode surface increases in surface area due to the formation of pores or pits, leading to a larger contact area with the electrolyte and consequently a lower DC internal resistance. Compared to Comparative Example 1, Example 1 showed comparable retention rates after 300 cycles, suggesting that excessively low Cr8O loading... 21 The coating is insufficient to form effective pores or pits for cycling on the lithium metal surface through pre-discharge; Example 3, compared to Example 2, shows that with surface Cr8O... 21 The increased load leads to more pores on the lithium metal surface after pre-discharge, resulting in lower internal resistance, but it does not further improve cycle life. This may be due to the presence of Cr8O. 21 The coating exhibits increased irreversible phase transitions during later cycles, affecting the battery's cycle stability and causing a rapid decline in capacity retention. In Comparative Example 2, although a Cr8O21 coating was present, the cycle life was not improved without low-current activation. In Comparative Example 3, no coating was applied, but low-current discharge activation was performed; neither the internal resistance nor the cycle life showed significant changes, indicating that the lithium-rich cathode ternary material, already in a reduced state, did not undergo lithium intercalation to guide the stripping of lithium metal from the anode. In Comparative Example 4, compared to Example 1, the coating underwent rolling and activation, resulting in a similarly reduced internal resistance and cycle life. The improvement in Comparative Example 1 is likely due to the tighter bonding of the active material after coating roll forming, leading to more uniform pit formation of lithium metal at the negative electrode after low-current activation. In Comparative Example 5, the coating contains unreacted CrO3, resulting in a significant increase in internal resistance and a significant decrease in cycle life after activation. This indicates that the unreacted CrO3 increases side reactions with the electrolyte during cycling, leading to a substantial decrease in battery life. In Comparative Example 6, the coating contains impurities. Although the internal resistance decreases after activation and can induce pit formation on the negative electrode, the cycle life is not significantly improved. This may be due to the presence of impurities, which reduces the Cr8O content in the coating. 21 Reduced activity and failure to form an effective negative electrode pit structure; from Figure 2 As can be seen, after 300 cycles, the cycle life of the battery cell in the example is improved compared to the comparative example, indicating that coating the electrode surface with high specific capacity Cr8O 21 The pre-discharge induced lithium metal pre-stripping strategy has a significant effect on improving battery cycle life.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0083] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for pre-stripping lithium metal anodes based on chromium oxide-coated multidimensional electrodes, characterized in that, include: Cr8O is deposited on the surface of the positive electrode substrate. 21 Active material layer, Cr8O was prepared 21 Coated multidimensional positive electrode; Cr8O 21 The coated multidimensional positive electrode, lithium metal negative electrode, electrolyte and separator are assembled to obtain a secondary lithium metal full cell; The secondary lithium metal full cell is subjected to a first low-current discharge activation treatment to generate uniformly distributed pits and / or active sites on the surface of the lithium metal anode.

2. The method for pre-stripping lithium metal anodes based on chromium oxide-coated multidimensional electrodes according to claim 1, characterized in that, At least one of the following conditions must be met: a. The material of the positive electrode substrate includes one or more of lithium manganese oxide, lithium iron phosphate, lithium cobalt oxide, nickel-cobalt-manganese ternary materials, and nickel-cobalt-aluminum ternary materials; b. The lithium metal anode includes one of lithium foil, lithium alloy foil, or lithium-based composite anode; c. The electrolyte includes one of carbonate electrolytes, ether electrolytes, or ionic liquid electrolytes; d. The diaphragm comprises one or more of polypropylene, polyimide, polybenzimidazole, cellulose nonwoven fabric, polyvinylidene fluoride porous membrane, and polyethylene.

3. The method for pre-stripping lithium metal anodes based on chromium oxide-coated multidimensional electrodes according to claim 1, characterized in that, The Cr8O 21 The active material was prepared by a high-temperature solid-state method, using CrO3 as a precursor and pyrolyzing it at 270℃-290℃.

4. The method for pre-stripping lithium metal anodes based on chromium oxide-coated multidimensional electrodes according to claim 3, characterized in that, At least one of the following conditions must be met: e. The Cr8O 21 The particle size of the active material is 50-10000 nm; f. The Cr8O 21 The coating thickness of the active material is 0.5-20 μm, and the coating amount is 5%-20% of the mass of the positive electrode substrate material.

5. The method for pre-stripping lithium metal anodes based on chromium oxide-coated multidimensional electrodes according to claim 1, characterized in that, The multidimensional positive electrode has a hierarchical porous structure, wherein the macropores formed by the accumulation of positive electrode substrate material particles have a diameter of 50-500 nm, and the Cr8O 21 The mesopores formed by the coating have a diameter of 10-50 nm.

6. The method for pre-stripping lithium metal anodes based on chromium oxide-coated multidimensional electrodes according to claim 2, characterized in that, The thickness of the lithium metal anode is 10-500 μm.

7. The method for pre-stripping lithium metal anodes based on chromium oxide coated multidimensional electrodes according to claim 2, characterized in that, The electrolyte also includes lithium salt; the amount of lithium salt added is 0.1%-5% of the total mass of the electrolyte. The lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(oxalate-borate), lithium difluorooxalate-borate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide.

8. The method for pre-stripping lithium metal anodes based on chromium oxide-coated multidimensional electrodes according to any one of claims 1-7, characterized in that, The conditions for the initial low-current discharge activation are as follows: cell ambient temperature 25-60℃, cell restraint pressure 20-200kPa, discharge current density 0.005-0.2C, discharge cutoff voltage 1.5-2.5V, discharge mode is constant current discharge, and discharge time is 1-5 h.

9. A lithium metal battery, characterized in that, The method for preparing the lithium metal battery includes the lithium metal anode pre-stripping method based on chromium oxide coated multidimensional electrodes as described in any one of claims 1-8.

10. An electrical-related device, characterized in that, Including the lithium metal battery as described in claim 9.

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