Self-generated negative electrode lithium metal solid-state battery and application thereof

Abstract

The application discloses a self-generated negative lithium metal solid-state battery and application. The battery comprises a positive electrode sheet, a negative electrode current collector and a low-liquid-gel solid-state electrolyte layer. The positive electrode sheet comprises a lithium-rich manganese-based positive electrode material. The negative electrode current collector comprises a copper foil substrate, an alloyable metal capacity calibration layer and a carbon plating layer. The ratio of the first circle additional lithium release capacity Q1 of the positive electrode sheet per unit area to the theoretical lithium receiving capacity Q2 of the alloyable metal capacity calibration layer per unit area is controlled to be 1.15-1.45. In combination with the first high-voltage formation and the subsequent lower upper limit voltage cycle, the active lithium released in the first formation process is alloyed and received on the negative electrode side and initial lithium deposition is completed. The structure is beneficial to improving the stability, cycle capacity retention capability and interface stability of the negative electrode self-generation process, and can be applied to high-specific-energy secondary batteries, battery modules or battery packs.

Description

Technical Field

[0001] This invention relates to the technical field of lithium secondary batteries, and in particular to a self-generating negative electrode lithium metal solid-state battery and its application. Background Technology

[0002] With increasing demands for energy density, safety, and cycle life in power batteries and energy storage systems, lithium metal anodes have become an important research direction for high-energy-density rechargeable batteries due to their high theoretical specific capacity and low electrode potential. Compared to batteries with pre-set lithium metal anodes, lithium metal batteries without anodes or with self-generated anodes do not pre-fill with excess lithium metal during assembly. Typically, lithium ions released from the positive electrode during the first charge deposit on the surface of the negative electrode current collector to form a lithium metal anode layer. Therefore, they have the potential to reduce the amount of lithium metal used on the negative electrode side and improve the battery's mass energy density and volumetric energy density.

[0003] Existing technologies have led to various improvements in negative electrode-free lithium metal batteries. For example, CN114284567A discloses a method for preparing a high-energy-density negative electrode-free lithium metal battery. This method involves preparing a positive electrode sheet containing lithium-rich materials, preparing and modifying the negative electrode current collector, assembling it with a separator and electrolyte, and then activating it to obtain a negative electrode-free lithium metal battery. This approach utilizes the irreversible lithium delithiation capacity during the first charge-discharge process of the lithium-rich material to compensate for the irreversible lithium loss on the negative electrode side, thereby extending the battery's cycle life. Another example is CN113013417A, which discloses a negative electrode-free lithium metal battery, its negative electrode current collector, and its preparation method. This method involves loading an ion-conducting layer, an electronic conductor layer, or an ion-electron hybrid conductor layer onto the negative electrode current collector substrate, giving the negative electrode current collector lithium-affinity properties or a lower nucleation barrier when alloyed with lithium, thereby improving lithium deposition behavior and cycle performance. The above technologies demonstrate that supplementing the positive electrode with an active lithium source or improving the lithium deposition process by modifying the surface of the current collector on the negative electrode side are both important ways to improve the performance of electrodeless lithium metal batteries.

[0004] However, the operation of electrodeless or self-generated negative electrode lithium metal batteries still faces significant interfacial stability issues. During the initial charge and subsequent cycles, lithium ions released from the positive electrode need to be converted into a reversibly deposited / stripped lithium metal layer on the surface of the negative electrode current collector. If the lithium deposition process on the negative electrode side is not coordinated with the interfacial film formation process, it can easily lead to continuous consumption of active lithium, exacerbation of electrolyte interfacial side reactions, and increased cycle impedance. Related research also indicates that when lithium metal deposition in electrodeless lithium metal batteries forms a high specific surface area morphology, it further intensifies the irreversible reaction between lithium and the electrolyte, leading to "dead lithium" and loss of active lithium, which in turn causes rapid capacity decay.

[0005] Therefore, existing self-generated lithium metal anode batteries, without pre-placing lithium metal at the initial anode, still need to reduce the impact of active lithium loss and interfacial side reaction accumulation on cycle stability during the initial anode formation and subsequent cycles. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned problems existing in the prior art and provide a self-generating lithium metal anode solid-state battery and its application, so that the solid-state battery without pre-placed lithium metal at the anode can stably form a lithium metal anode during the first formation process, and improve the utilization efficiency and interface stability of active lithium during subsequent cycles.

[0007] To achieve the above objectives, the first aspect of the present invention provides a self-generating negative electrode lithium metal solid battery, comprising a positive electrode sheet, a negative electrode current collector, and a low-electrolyte gel solid electrolyte layer. The positive electrode sheet includes a positive current collector and a positive active layer disposed on the surface of the positive current collector, wherein the positive active layer includes a lithium-rich manganese-based positive electrode material; The negative electrode current collector includes a copper foil substrate, an alloyable metal capacity calibration layer disposed on the surface of the copper foil substrate, and a carbon plating layer covering the alloyable metal capacity calibration layer. The low-precipitate gel solid electrolyte layer includes a cross-linked polymer network and DMM and LiFSI retained in the cross-linked polymer network; The additional lithium release capacity per unit area in the first cycle of the lithium-rich manganese-based cathode material is denoted as Q1, and the theoretical lithium receiving capacity per unit area of ​​the alloyable metal capacity calibration layer is denoted as Q2. The ratio of Q1 to Q2 is 1.15 to 1.45. The highest initial formation voltage of the self-generated negative electrode lithium metal solid-state battery is 4.55–4.70V, and the upper limit voltage of subsequent cycles is 0.15–0.25V lower than the highest initial formation voltage. Wherein, Q1 is the first-cycle irreversible capacity per unit area obtained by charging the positive electrode to 4.60V at 0.05C and then discharging it to 2.00V at 0.05C in a lithium half-cell; Q2 represents the theoretical lithium receiving capacity per unit area of ​​the alloyable metal capacity calibration layer, which is calculated according to Faraday's law. Specifically, Q2 is calculated according to the following formula: In the formula, m is the mass of the alloyable metal in the alloyable metal capacity calibration layer, in g; n is the number of lithium moles consumed when each mole of the alloyable metal is converted into the corresponding lithium alloy phase; F is the Faraday constant, taken as 96485 C / mol; M is the molar mass of the alloyable metal, in g / mol; and S is the area of ​​the alloyable metal capacity calibration layer, in cm². 2 .

[0008] In the above technical solution, the additional active lithium released by the lithium-rich manganese-based cathode material during the first high-voltage formation stage no longer manifests solely as irreversible capacity loss on the cathode side, but is instead used to construct the initial lithium source on the anode side. The alloyable metal capacity calibration layer, through an alloying reaction with this portion of active lithium, forms an initial receiving interface with lithium affinity on the copper foil substrate surface. The carbon coating further provides a continuous electron transport path and interface coverage structure, enabling lithium ions to obtain a more uniform nucleation base during reduction deposition on the anode side. Thus, in a battery where no metallic lithium is initially placed on the anode, a self-generated lithium metal anode interface can be formed during the first formation process through lithium release from the cathode, alloying reception on the anode, and initial lithium deposition.

[0009] By controlling the Q1 / Q2 ratio to 1.15–1.45, the alloyable metal capacity calibration layer can fully participate in the alloying reaction during the initial formation stage. After alloying acceptance, a suitable amount of active lithium is retained for initial lithium metal deposition, thus forming a composite anode interface composed of the alloying acceptance interface, the carbon plating interface, and the initial lithium deposition interface. This composite anode interface can simultaneously play a role in capacity buffering, nucleation induction, and electron transport homogenization, providing a clear capacity constraint and interface induction path for the initial anode formation process. This is beneficial for improving the consistency of self-generated anode formation, the uniformity of lithium deposition, and the lithium utilization efficiency in subsequent cycling processes.

[0010] The initial formation voltage is controlled at 4.55–4.70V, allowing the lithium-rich manganese-based cathode material to fully release additional active lithium for anode self-generation during the initial formation stage. Subsequent cycling voltage limits are 0.15–0.25V lower than the initial formation voltage, enabling the battery to enter a voltage range more suitable for long-term cycling after initial anode interface construction. This voltage control allows the initial formation stage to handle additional lithium release from the cathode, anode alloying reception, and initial deposition interface construction, while subsequent cycling stages primarily focus on reversible lithium deposition and stripping around the formed anode interface. This approach effectively balances anode formation efficiency, cathode capacity utilization, and cycle stability.

[0011] Preferably, the general chemical formula of the lithium-rich manganese-based cathode material is xLi2MnO3·(1-x)LiMO2, where 0.25≤x≤0.55, M includes at least two elements selected from Ni, Co, Mn, Al, Mg, and Ti, and Mn accounts for 55% to 85% of the total molar amount of transition metal elements in the lithium-rich manganese-based cathode material.

[0012] By defining the composition of the lithium-rich manganese-based cathode material as described above, the Li2MnO3 component can provide a stable additional lithium release source during the initial high-voltage formation stage, while the LiMO2 component helps maintain the reversible capacity contribution and layered structure stability of the cathode material. A ratio of 0.25 ≤ x ≤ 0.55 balances the additional lithium release capacity with subsequent cycle reversibility, and the Mn element accounting for 55%–85% of the total molar amount of transition metal elements is beneficial for improving the capacity contribution and structural support of the material system.

[0013] Preferably, the positive electrode active layer comprises the following components in weight percentage: 90%–96% lithium-rich manganese-based positive electrode material, 1.5%–5% conductive agent, and 2.5%–5% binder; the single-sided areal capacity of the positive electrode active layer is 3.0–5.5 mAh / cm². 2 Q1 is 0.30~1.20mAh / cm³. 2 .

[0014] By limiting the positive electrode active layer ratio and areal capacity as described above, the positive electrode sheet can form a stable electron transport network and electrode bonding structure while maintaining a high proportion of active materials. Controlling the percentage of lithium-rich manganese-based positive electrode material at 90%–96% is beneficial for improving the unit area capacity and energy density; controlling the percentage of conductive agent at 1.5%–5% is beneficial for improving the continuity of electron transport during the high-voltage formation stage; and controlling the percentage of binder at 2.5%–5% is beneficial for maintaining the structural integrity of the positive electrode active layer during the initial formation and cycling processes. The single-sided areal capacity is 3.0–5.5 mAh / cm². 2 Q1 is 0.30~1.20mAh / cm³ 2 This ensures that the amount of additional active lithium released by the positive electrode is within a range suitable for area capacity matching with the thin alloyable metal capacity calibration layer, thereby improving the controllability of the negative electrode self-generation process.

[0015] Preferably, the alloyable metal capacity calibration layer includes one or more of Sn, Ag, Mg, and Zn; when the alloyable metal is Sn, the corresponding lithium alloy phase is determined according to Li... 4.4 Sn is calculated; when the alloyable metal is Ag, the corresponding lithium alloy phase is calculated as LiAg; when the alloyable metal is Zn, the corresponding lithium alloy phase is calculated as LiZn; when the alloyable metal is Mg, the corresponding lithium alloy phase is calculated as Li3Mg.

[0016] By defining the types of alloyable metals and their corresponding lithium alloy phases, the lithium-accepting capacity of the alloyable metal capacity calibration layer has a clear stoichiometric basis. Sn, Ag, Mg, and Zn can all form corresponding lithium alloy phases with lithium. Their alloying process can create lithium-affinity accepting sites on the copper foil substrate surface, transforming the negative electrode surface from a common metal current-collecting interface into a composite interface suitable for lithium nucleation and deposition. Simultaneously, by calculating the theoretical lithium-accepting capacity using the corresponding lithium alloy phase, the role of the negative electrode surface layer can be transformed from simple material selection into capacity calibration, establishing a calculable matching relationship between it and the initial additional lithium release capacity of the positive electrode, thereby improving the consistency of the initial interface construction of the negative electrode in different batches of batteries.

[0017] Preferably, the thickness of the alloyable metal capacity calibration layer is 0.35–1.40 μm, and the unit area mass of the alloyable metal capacity calibration layer is 0.25–1.00 mg / cm³. 2 Q2 is 0.25~1.00mAh / cm³. 2 The carbon coating includes one of an amorphous carbon layer, a nitrogen-doped carbon layer, and a graphitized carbon layer. The thickness of the carbon coating is 50–300 nm, and the sheet resistivity of the carbon coating is 0.8–10 Ω / sq.

[0018] By defining the thickness, unit area mass, and Q2 range as described above, a thin, lithium-loving metal layer is formed on the surface of the negative electrode current collector using an alloyable metal capacity calibration layer. This metal layer is not used as the primary lithium storage negative electrode, but rather to receive a portion of the active lithium released from the positive electrode during the initial formation process, forming a lithium alloy phase with this portion of active lithium. Due to the small thickness and unit area mass of this layer, the amount of active lithium it consumes can be accurately limited by Q2, preventing excessive active lithium from remaining in the alloying reaction. Simultaneously, this layer provides a sufficient number of alloying acceptor sites, transforming the copper foil substrate surface into a more suitable lithium-loving interface for lithium deposition.

[0019] Q2 is 0.25~1.00mAh / cm³. 2 In this process, the alloyable metal capacity calibration layer can effectively match the initial additional lithium release capacity of the positive electrode. During the first formation, the active lithium released from the positive electrode side first undergoes alloying and acceptance in this capacity calibration layer, resulting in a relatively uniform lithium-containing alloy region on the negative electrode surface. Subsequently, the remaining active lithium continues to deposit near this lithium-containing alloy region, forming the initial lithium metal layer. Thus, lithium metal is not deposited directly and randomly on the copper foil surface, but rather formed at the interface after capacity calibration and lithiophilic induction, which helps to improve the controllability of the initial lithium deposition location and deposition amount.

[0020] Secondly, after the carbon coating covers the surface of the alloyable metal capacity calibration layer, a continuous conductive coating layer can be formed on the surface of the negative electrode current collector. When the carbon coating thickness is 50–300 nm and the sheet resistivity is 0.8–10 Ω / sq, it can maintain good electron transport continuity without forming an excessively thick barrier layer that would affect the arrival of lithium ions at the alloyable metal capacity calibration layer. This carbon coating makes the electron distribution on the negative electrode surface more uniform, making the lithium ion reduction and deposition conditions in different regions more consistent, thereby promoting uniform nucleation and deposition of lithium in the negative electrode planar direction.

[0021] Therefore, when the alloyable metal capacity calibration layer is combined with the carbon coating, the former mainly addresses the issues of lithium acceptance and induced nucleation on the anode surface, while the latter mainly addresses the issues of electron transport uniformity and interface continuity on the anode surface. Together, they transform the anode interface formed during the initial formation process from a typical copper foil interface into a composite interface with capacity acceptance, lithiophilic induction, and conductivity homogenization functions. This facilitates the formation of a more uniform and stable self-generated lithium metal anode and improves the stability of lithium deposition and stripping during subsequent cycles.

[0022] Preferably, the low-leakage gel solid electrolyte layer has a leakage rate of no more than 3% after standing at 0.2 MPa pressure for 30 min, a mass loss rate of no more than 8% after standing at 60℃ for 24 h, and an ionic conductivity of 0.5 to 5.0 mS / cm at 25℃.

[0023] Under the constraints of the aforementioned liquid precipitation rate, mass loss rate, and ionic conductivity, the gel-solid electrolyte layer maintains a stable gel morphology under pressure and temperature, and continuously provides high lithium-ion transport capacity. For systems where metallic lithium is not initially pre-placed at the negative electrode, the negative electrode interface formed during the initial formation stage is highly sensitive to ion flux and electrolyte contact state. This gel-solid electrolyte layer exhibits a low liquid precipitation rate under pressure, enabling DMM and LiFSI to be more uniformly maintained within the cross-linked polymer network, reducing local enrichment or deficiency of electrolyte components on the negative electrode surface. Simultaneously, this gel-solid electrolyte layer possesses a low thermal mass loss rate and high ionic conductivity, maintaining a stable solvation environment and continuous lithium-ion transport channels during the initial formation and subsequent cycling processes. Therefore, lithium ions can reach the negative electrode current collector surface more uniformly, allowing alloying reception, initial lithium deposition, and interfacial film formation processes to occur under stable electrolyte contact conditions, thereby improving the compactness and cycle retention capacity of the self-generated negative electrode interface.

[0024] Preferably, the crosslinked polymer network is formed from one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, polyacrylonitrile, and polymethyl methacrylate; DMM accounts for 70% to 95% of the total mass of non-aqueous solvent in the low-elution gel solid electrolyte layer, and the concentration of LiFSI in the low-elution gel solid electrolyte layer is 1.8 to 3.2 mol / L.

[0025] By defining the cross-linked polymer network, DMM, and LiFSI content, the gel solid electrolyte layer possesses structural retention, solvation regulation, and interfacial film formation capabilities. The cross-linked polymer network restricts the free migration of DMM-type solvents, ensuring a relatively stable spatial distribution of the electrolyte layer under conditions of formation pressure, cycling temperature variations, and electrode volume changes. DMM constitutes 70%–95% of the total non-aqueous solvent mass, which is beneficial for improving the lithium salt dissolution state and lithium ion migration. A LiFSI concentration of 1.8–3.2 mol / L facilitates the formation of a solvation environment with a high lithium salt concentration and promotes the formation of a stable interfacial film involving fluorine and sulfur components on the negative electrode side. This interfacial film, combined with the lithiophilic interface formed by the alloyable metal capacity calibration layer, provides both a nucleation-inducing basis and a stable film formation environment on the negative electrode side.

[0026] Preferably, the low-precipitate gel solid electrolyte layer further includes an oxide solid electrolyte filler, wherein the oxide solid electrolyte filler includes Li7La3Zr2O 12 Li 1.3 Al0.3Ti 1.7 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 One or more of (PO4)3 and Li3PO4 are used to coat alumina, and the oxide solid electrolyte filler accounts for 5% to 30% of the total mass of the low-precipitate gel solid electrolyte layer.

[0027] By incorporating the aforementioned oxide solid electrolyte filler, the gel solid electrolyte layer achieves better dimensional stability, compressive strength retention, and interfacial support. After being dispersed within the cross-linked polymer network, the oxide solid electrolyte filler forms an inorganic support phase, enhancing the gel layer's structural retention under stacking pressure and cycling processes, and improving the continuity of lithium-ion transport within the gel layer. Maintaining a filler content of 5%–30% helps achieve a balance between flexible adhesion, ion transport, and mechanical support in the gel layer, ensuring stable contact between the positive electrode, the low-electrolyte gel solid electrolyte layer, and the negative electrode current collector, thereby promoting the stable formation and continuous operation of the self-generated lithium metal negative electrode interface.

[0028] Preferably, the initial formation of the self-generated negative electrode lithium metal solid-state battery includes the following steps: S1: Charge to 4.30-4.45V at 0.02C-0.05C; S2: Continue charging at 0.05C to 0.10C until 4.55 to 4.70V; S3: Charge at a constant voltage of 4.55 to 4.70V until the current drops to 0.01C to 0.05C; S4: Discharge to 2.00-2.50V at 0.05C-0.10C; The upper limit voltage for subsequent cycles is 4.30–4.50V.

[0029] Through the aforementioned initial formation steps, the additional lithium release from the positive electrode, the alloying and acceptance of the negative electrode, and the initial lithium deposition can proceed in an orderly manner along a relatively mild electrochemical pathway. Stage S1, charging at a low rate to 4.30–4.45V, is beneficial for establishing a stable electrode polarization state. Stage S2, continuing charging to 4.55–4.70V, is beneficial for triggering the additional lithium release process of the lithium-rich manganese-based positive electrode material. Stage S3, maintaining a constant voltage at high voltage until the current decreases, is beneficial for the released lithium to fully complete alloying and initial deposition rearrangement on the negative electrode side. Stage S4, discharging at a low rate, is beneficial for balancing the electrode state after the initial formation. The subsequent cycle upper limit voltage is 4.30–4.50V, allowing the battery to enter a stable cycling range after completing the self-generated negative electrode interface construction, thereby improving capacity retention and interface stability during long-term cycling.

[0030] A second aspect of the present invention provides an application of the above-mentioned self-generated negative electrode lithium metal solid-state battery in high-energy-density secondary batteries, battery modules, or battery packs.

[0031] In the aforementioned applications, this self-generating lithium metal solid-state battery does not pre-place lithium metal in the initial state of the negative electrode, which simplifies the prefabrication, transfer, and assembly process of the lithium metal negative electrode and improves consistency in the battery manufacturing process. Through the synergistic cooperation of the additional lithium release capacity in the first cycle of the positive electrode, the alloyable metal capacity calibration layer, the carbon coating, the low-electrolysis gel solid electrolyte layer, and the first formation process, the battery can form a stable self-generating negative electrode interface under high areal capacity conditions, making it suitable for secondary battery systems with high requirements for mass energy density, cycle stability, and manufacturing consistency.

[0032] The present invention, by adopting the above technical solution, has the following beneficial effects: 1. This invention utilizes the additional active lithium generated during the first high-voltage formation stage of lithium-rich manganese-based cathode material as the initial lithium source on the anode side, and uses an alloyable metal capacity calibration layer for capacity reception and interface induction, enabling solid-state batteries without pre-placed metallic lithium on the anode to form a stable self-generated lithium metal anode interface during the first formation process.

[0033] 2. This invention controls the additional lithium release capacity Q1 per unit area of ​​the positive electrode sheet in the first cycle and the theoretical lithium receiving capacity Q2 per unit area of ​​the alloyable metal capacity calibration layer to be 1.15 to 1.45, so that a synergistic matching relationship is formed between the lithium release amount on the positive electrode side, the alloy receiving amount on the negative electrode side and the initial lithium deposition amount, thereby improving the controllability of the first negative electrode formation process, the consistency of the negative electrode interface formation and the lithium utilization efficiency in subsequent cycles.

[0034] 3. This invention constructs a composite negative electrode current collector surface by combining an alloyable metal capacity calibration layer and a carbon coating, enabling the negative electrode side to simultaneously possess lithium-affinity nucleation sites and a continuous electron transport interface. The alloyable metal layer provides a defined lithium receiving capacity and an alloying receiving basis, while the carbon coating provides electron transport homogenization and interface coverage. Together, they promote uniform lithium metal deposition and reversible stripping.

[0035] 4. This invention maintains a stable bond between DMM, LiFSI and cross-linked polymer networks through a low-precipitate gel solid electrolyte layer, and maintains a relatively stable gel morphology under pressure and temperature. This allows for continuous lithium-ion transport channels and a stable interfacial film-forming environment during the self-generation of the negative electrode, thereby improving the stability of the self-generated negative electrode interface and the battery cycle retention capability.

[0036] 5. This invention enables the additional lithium release characteristics of lithium-rich manganese-based cathode materials to be fully utilized in the first formation stage by differentially controlling the highest voltage of the first formation and the upper limit voltage of subsequent cycles, and enables stable lithium deposition and stripping around the formed negative electrode interface in the subsequent cycle stage, thereby taking into account the self-generation efficiency of the negative electrode, the capacity utilization of the positive electrode and the long-term cycle stability.

[0037] 6. The positive electrode lithium release capacity, negative electrode alloy receiving capacity, carbon coating electron homogenization interface, low precipitation gel solid electrolyte layer and segmented formation process of the present invention work together to enable the solid battery to obtain a stable negative electrode interface without pre-placing a metallic lithium negative electrode, providing a structural and process basis for improving the manufacturing consistency, capacity retention and safety of high-energy-density secondary batteries, battery modules and battery packs. Detailed Implementation

[0038] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0039] Unless otherwise defined, all scientific and technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art.

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0042] The present invention will now be described in detail with reference to specific embodiments, which are intended to understand rather than limit the invention.

[0043] Example 1 This embodiment discloses a self-generated negative electrode lithium metal solid battery, including a positive electrode sheet, a negative electrode current collector, and a low-electrolyte gel solid electrolyte layer. The specific preparation process is as follows.

[0044] S1. Prepare the positive electrode sheet.

[0045] A lithium-rich manganese-based cathode material was selected as the cathode active material. The chemical composition of this lithium-rich manganese-based cathode material is 0.4Li₂MnO₃·0.6LiNi. 0.2 Co 0.1 Mn 0.65 Al 0.05 O2, D 50 The particle size is 8.5 μm, and the tap density is 2.3 g / cm³. 3 The moisture content is 420 ppm.

[0046] Weigh out 94.0% of lithium-rich manganese-based cathode material, 3.0% of conductive carbon black, and 3.0% of polyvinylidene fluoride (PVDF) binder by mass percentage. The conductive carbon black is acetylene black with an average primary particle size of 35 nm; the PVDF binder has a weight-average molecular weight of 800,000. Add the PVDF binder to N-methylpyrrolidone and stir at 25°C for 2 h to obtain a binder solution with a mass fraction of 6.0%. Add the conductive carbon black to the binder solution and disperse at 1500 r / min for 30 min. Then add the lithium-rich manganese-based cathode material and stir at 1000 r / min for 2 h to obtain the cathode slurry. The cathode slurry has a solid content of 58.0% and a viscosity of 5200 mPa·s at 25°C.

[0047] The positive electrode slurry was coated onto one side of a 12 μm thick aluminum foil current collector, resulting in a wet film thickness of 135 μm. After coating, it was pre-dried in hot air at 80℃ for 20 min, followed by vacuum drying at 120℃ for 10 h. The dried electrode sheet was then rolled to achieve a compaction density of 2.9 g / cm³ for the positive electrode active layer. 3 The single-sided capacity is 4.2mAh / cm².2 The positive electrode sheet is punched into pieces with an area of ​​100 cm². 2 The sheets are ready for use.

[0048] A lithium-ion half-cell was assembled using the same positive electrode and lithium foil. It was charged to 4.60V at 0.05C and then discharged to 2.00V at 0.05C. The measured irreversible capacity Q1 per unit area for the first cycle was 0.60 mAh / cm². 2 .

[0049] S2. Prepare the negative electrode current collector.

[0050] An 8 μm thick electrolytic copper foil was selected as the copper foil substrate. The copper foil substrate was sequentially ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 10 minutes each time, and then vacuum-dried at 60°C for 2 hours. The dried copper foil substrate was then placed in a magnetron sputtering apparatus and evacuated to a vacuum of 5.0 × 10⁻⁶. -4 When the pressure is below 0.5 Pa, argon gas is introduced until the working pressure is 0.5 Pa.

[0051] A Sn capacity calibration layer was deposited on one side of a copper foil substrate using a Sn target with a purity of 99.99%. The sputtering power was 120 W, the substrate temperature was 25 °C, and the deposition time was 18 min, resulting in a Sn capacity calibration layer with a thickness of 692 nm. The thickness was calibrated using a quartz crystal film thickness gauge and a step gauge, and the mass per unit area of ​​the Sn capacity calibration layer was measured to be 0.506 mg / cm² by weighing. 2 Sn according to Li 4.4 The calculation for Sn corresponds to n = 4.4. Assuming the molar mass of Sn is 118.71 g / mol, Q2 = (m × n × F) / (M × 3.6 × S), yielding a Q2 of 0.502 mAh / cm³. 2 Q1 / Q2 is 1.2.

[0052] After the Sn capacity calibration layer was deposited, a nitrogen-doped carbon layer was deposited on the surface of the Sn capacity calibration layer without disrupting the vacuum environment. Radio frequency sputtering was performed using a graphite target at a mixed atmosphere of argon and nitrogen (argon flow rate 40 sccm, nitrogen flow rate 4 sccm, working pressure 0.6 Pa, sputtering power 180 W, and deposition time 12 min), resulting in a nitrogen-doped carbon layer with a thickness of 180 nm. The resistivity of the carbon layer was measured to be 2.5 Ω / sq using the four-probe method.

[0053] S3. Prepare a low-precipitate gel solid electrolyte layer.

[0054] Weigh out 70 parts by weight of polyvinylidene fluoride-hexafluoropropylene copolymer, 20 parts of polymethyl methacrylate, 15 parts of Li7La3Zr2O12 oxide solid electrolyte filler, and 420 parts of N-methylpyrrolidone. The polyvinylidene fluoride-hexafluoropropylene copolymer has a hexafluoropropylene structural unit mass fraction of 12% and a weight-average molecular weight of 450,000; polymethyl methacrylate has a weight-average molecular weight of 350,000; and Li7La3Zr2O12 oxide solid electrolyte filler... 12 Packing D 50 The particle size is 500 nm.

[0055] Polyvinylidene fluoride-hexafluoropropylene copolymer and polymethyl methacrylate were added to N-methylpyrrolidone and stirred at 50°C for 4 hours to obtain a polymer solution. Li7La3Zr2O 12 The filler was added to the polymer solution and dispersed at 2000 r / min for 40 min, followed by vacuum degassing for 20 min to obtain a film-forming slurry. The film-forming slurry was coated onto a polytetrafluoroethylene release film with a wet film thickness of 120 μm. It was dried at 80 °C for 30 min and then vacuum dried at 100 °C for 6 h to obtain a porous polymer-supported film with a thickness of 32 μm.

[0056] Prepare the gel solution. The non-aqueous solvent consists of dimethoxymethane and fluoroethylene carbonate, with dimethoxymethane accounting for 85% of the total mass of the non-aqueous solvent and fluoroethylene carbonate accounting for 15%. Add lithium bis(fluorosulfonyl)imide to the non-aqueous solvent to make the lithium bis(fluorosulfonyl)imide concentration 2.5 mol / L. Add polyethylene glycol diacrylate and 2-hydroxy-2-methylphenylacetone to the lithium salt solution, with polyethylene glycol diacrylate accounting for 4.0% of the mass of the lithium salt solution and 2-hydroxy-2-methylphenylacetone accounting for 1.0% of the mass of polyethylene glycol diacrylate. Stir at 25°C for 30 min to obtain the gel solution.

[0057] In an environment with a dew point below -40°C, a porous polymer-supported membrane was immersed in a gel solution and soaked at 25°C for 20 min. After removal, the surface free liquid was scraped off with a polytetrafluoroethylene (PTFE) scraper. Subsequently, it was irradiated under 365 nm UV light for 8 min to crosslink polyethylene glycol diacrylate, retaining the liquid components containing dimethoxymethane and lithium bis(fluorosulfonyl)imide within the pores and crosslinked structure of the polymer-supported membrane, resulting in a low-leakage gel solid electrolyte layer. The thickness of the low-leakage gel solid electrolyte layer was 45 μm. Tests showed that the gel solid electrolyte layer had a leakage rate of 2.1% after standing at 0.2 MPa for 30 min, a mass loss rate of 5.6% after standing at 60°C for 24 h, and an ionic conductivity of 2.0 mS / cm at 25°C.

[0058] S4. Assemble the battery and perform the first formation.

[0059] In a dry environment with a dew point below -40°C, the positive electrode, a low-electrolyte gel solid electrolyte layer, and the negative electrode current collector are stacked sequentially, with the positive electrode active layer facing the gel solid electrolyte layer and the nitrogen-doped carbon layer facing the gel solid electrolyte layer. After stacking, a surface pressure of 0.2 MPa is applied and maintained for 10 minutes to ensure full interface adhesion. Subsequently, an aluminum-plastic film is used for encapsulation to obtain a pouch-type self-generated negative electrode lithium metal solid battery.

[0060] After encapsulation, the battery is left to stand for 12 hours, and then undergoes its first formation. The first formation includes the following steps: S1, Charge to 4.40V at 0.03C; S2, continue charging at 0.08C to 4.65V; S3, charge at a constant voltage of 4.65V until the current drops to 0.02C; S4, discharge to 2.20V at 0.08C.

[0061] After the first formation is completed, the upper limit voltage of the battery for subsequent cycles is 4.45V, and the discharge cutoff voltage is 2.20V.

[0062] In this embodiment, the additional active lithium released by the lithium-rich manganese-based cathode material during the first high-voltage formation stage matches the theoretical lithium-receiving capacity of the Sn capacity calibration layer. The Sn capacity calibration layer first receives some active lithium to form a lithium-containing alloy interface, the nitrogen-doped carbon layer provides a continuous electron transport path, and the low-electrolyte gel solid electrolyte layer provides a stable lithium-ion transport and interfacial contact environment, enabling the formation of a self-generated lithium metal anode interface on the surface of the anode current collector.

[0063] Example 2 This embodiment discloses a self-generated negative electrode lithium metal solid-state battery. Compared with Embodiment 1, the differences lie in the positive electrode sheet, Sn capacity calibration layer, carbon coating, gel solid electrolyte layer, and formation voltage parameters, as detailed below.

[0064] The positive electrode active material is 0.3Li₂MnO₃·0.7LiNi 0.25 Co 0.1 Mn 0.6 Al 0.05 O2, D 50 The particle size is 7.8 μm. By weight percentage, the positive electrode active layer comprises 95.0% lithium-rich manganese-based positive electrode material, 2.0% conductive carbon black, and 3.0% polyvinylidene fluoride binder. The single-sided areal capacity of the positive electrode active layer is 3.4 mAh / cm². 2 According to the lithium-ion half-cell test, Q1 is 0.36 mAh / cm³. 2 .

[0065] The Sn capacity calibration layer has a thickness of 428 nm and a mass per unit area of ​​0.313 mg / cm³.2 According to Li 4.4 The calculated Q2 of Sn is 0.311 mAh / cm2, and the Q1 / Q2 ratio is 1.16. The carbon coating is an amorphous carbon layer with a thickness of 120 nm and a sheet resistivity of 4.0 Ω / sq.

[0066] In the low-precipitate gel solid electrolyte layer, dimethoxymethane accounts for 80% of the total mass of the non-aqueous solvent, lithium bis(fluorosulfonyl)imide concentration is 2.2 mol / L, and the oxide solid electrolyte filler is Li. 1.3 Al 0.3 Ti 1.7 (PO4)3, the filler accounts for 10% of the total mass of the low-exudate gel solid electrolyte layer. The gel solid electrolyte layer thickness is 43 μm, the exudate rate is 2.5%, the mass loss rate at 60℃ is 6.3%, and the ionic conductivity at 25℃ is 1.6 mS / cm.

[0067] During the initial formation, the battery was charged at 0.03C to 4.35V, then charged at 0.08C to 4.60V, and then charged at a constant voltage of 4.60V until the current dropped to 0.02C. Finally, it was discharged at 0.08C to 2.20V. The upper limit voltage for subsequent cycles was 4.40V, and the discharge cutoff voltage was 2.20V. The remaining materials, operating procedures, and battery assembly methods were consistent with Example 1.

[0068] Example 3 This embodiment discloses a self-generated negative electrode lithium metal solid-state battery. Compared with Embodiment 1, the differences lie in the positive electrode sheet, Sn capacity calibration layer, carbon coating, gel solid electrolyte layer, and formation voltage parameters, as detailed below.

[0069] The positive electrode active material is 0.5Li₂MnO₃·0.5LiNi. 0.15 Co 0.1 Mn 0.7 Mg 0.05 O2, D 50 The particle size is 9.2 μm. By weight percentage, the positive electrode active layer comprises 92.0% lithium-rich manganese-based positive electrode material, 4.0% conductive carbon black, and 4.0% polyvinylidene fluoride binder. The single-sided areal capacity of the positive electrode active layer is 5.0 mAh / cm². 2 Based on lithium-ion half-cell testing, Q1 has a capacity of 1.05 mAh / cm³. 2 .

[0070] The Sn capacity calibration layer has a thickness of 1186 nm and a mass per unit area of ​​0.868 mg / cm³. 2 According to Li 4.4 Sn calculates Q2 to be 0.861 mAh / cm³. 2Q1 / Q2 is 1.22. The carbon coating is a graphite-like carbon layer, formed by radio frequency sputtering of a graphite target at 25°C, with a thickness of 240nm and a sheet resistivity of 1.2Ω / sq.

[0071] In the low-precipitate gel solid electrolyte layer, dimethoxymethane accounts for 90% of the total mass of the non-aqueous solvent, lithium bis(fluorosulfonyl)imide concentration is 2.8 mol / L, and the oxide solid electrolyte filler is Li7La3Zr2O. 12 The filler accounts for 20% of the total mass of the low-exudate gel solid electrolyte layer. The gel solid electrolyte layer has a thickness of 48 μm, an exudate rate of 1.7%, a mass loss rate of 4.9% at 60℃, and an ionic conductivity of 2.4 mS / cm at 25℃.

[0072] During the initial formation, the battery was charged at 0.02C to 4.45V, then charged at 0.06C to 4.70V, and then charged at a constant voltage of 4.70V until the current dropped to 0.02C. Finally, it was discharged at 0.06C to 2.30V. The upper limit voltage for subsequent cycles was 4.50V, and the discharge cutoff voltage was 2.30V. The remaining materials, operating procedures, and battery assembly methods were consistent with Example 1.

[0073] Example 4 This embodiment discloses a self-generated negative electrode lithium metal solid-state battery. Compared with Embodiment 1, the difference lies in that the alloyable metal capacity calibration layer adopts a Sn-Mg composite metal layer, and the Q1 of the positive electrode is adjusted accordingly, as follows.

[0074] The positive electrode active material is 0.48Li₂MnO₃·0.52LiNi. 0.16 Co 0.1 Mn 0.69 Al 0.05 O2. The positive electrode active layer contains 93.5% lithium-rich manganese-based positive electrode material, 3.0% conductive carbon black, and 3.5% polyvinylidene fluoride binder. The single-sided areal capacity of the positive electrode active layer is 4.7 mAh / cm². 2 According to the lithium-ion half-cell test, Q1 has a capacity of 0.88 mAh / cm³. 2 .

[0075] A Sn-Mg composite metal layer was deposited on a copper foil substrate using co-sputtering with Sn and Mg targets. The Sn target purity was 99.99%, and the Mg target purity was 99.95%. The sputtering power of the Sn target was 90 W, and that of the Mg target was 45 W. The working pressure was 0.5 Pa, the substrate temperature was 25 °C, and the deposition time was 24 min, resulting in a Sn-Mg composite metal layer with a thickness of 836 nm. The mass ratio of Sn to Mg in this composite metal layer was 70:30, and the mass per unit area was 0.451 mg / cm³. 2 The mass of Sn per unit area is 0.316 mg / cm³.2 The mass of Mg per unit area is 0.135 mg / cm³. 2 Li is formed according to Sn. 4.4 Calculations based on the formation of Li3Mg from Sn and Mg show that Q2 is 0.761 mAh / cm³. 2 Q1 / Q2 is 1.16.

[0076] After the Sn-Mg composite metal layer was deposited, without exposing air, an amorphous carbon layer was deposited on the surface of the Sn-Mg composite metal layer. The amorphous carbon layer had a thickness of 200 nm and a sheet resistivity of 2.2 Ω / sq. The low-electrolyte gel solid electrolyte layer and battery assembly steps were the same as in Example 1. The highest voltage at the first formation was 4.65 V, the upper limit voltage for subsequent cycles was 4.45 V, and the discharge cutoff voltage was 2.20 V.

[0077] Example 5 This embodiment discloses a self-generated negative electrode lithium metal solid-state battery. Compared with Embodiment 1, the difference is that the alloyable metal capacity calibration layer adopts a Zn capacity calibration layer, and the Q1 of the positive electrode is adjusted accordingly, as follows.

[0078] The positive electrode active material is 0.32Li₂MnO₃·0.68LiNi. 0.24 Co 0.1 Mn 0.61 Ti 0.05 O2. The positive electrode active layer contains 94.5% lithium-rich manganese-based positive electrode material, 2.5% conductive carbon black, and 3.0% polyvinylidene fluoride binder. The single-sided areal capacity of the positive electrode active layer is 3.8 mAh / cm². 2 According to the lithium-ion half-cell test, Q1 is 0.45 mAh / cm³. 2 .

[0079] A Zn capacity calibration layer was deposited on a copper foil substrate using a Zn target with a purity of 99.99%. The sputtering power was 110 W, the operating pressure was 0.5 Pa, the substrate temperature was 25 °C, and the deposition time was 28 min, resulting in a Zn capacity calibration layer with a thickness of 1238 nm. The mass per unit area of ​​the Zn capacity calibration layer was 0.885 mg / cm³. 2 Zn is calculated as LiZn, corresponding to n=1. The molar mass of Zn is calculated as 65.38 g / mol, and Q2 is 0.363 mAh / cm³. 2 Q1 / Q2 is 1.24.

[0080] After the Zn capacity calibration layer was deposited, without exposing the air, a nitrogen-doped carbon layer was deposited on the surface of the Zn capacity calibration layer. The nitrogen-doped carbon layer had a thickness of 180 nm and a sheet resistivity of 3.0 Ω / sq. The low-electrolyte gel solid electrolyte layer and battery assembly steps were the same as in Example 1. The highest voltage at the first formation was 4.60 V, the upper limit voltage for subsequent cycles was 4.40 V, and the discharge cutoff voltage was 2.20 V.

[0081] Example 6 This embodiment discloses a self-generated negative electrode lithium metal solid-state battery. Compared with Embodiment 1, the difference lies in the type and content of oxide solid electrolyte filler in the low-electrolyte gel solid electrolyte layer, as detailed below.

[0082] In the low-precipitate gel solid electrolyte layer, the oxide solid electrolyte filler is Li3PO4 coated with alumina. The D of Li3PO4 coated alumina... 50 The particle size is 300 nm, and the Li3PO4 coating layer accounts for 8% of the total mass of the filler. This filler accounts for 5% of the total mass of the low-precipitate gel solid electrolyte layer.

[0083] In preparing the polymer-supported membrane, Li3PO4-coated alumina was added to a solution of polyvinylidene fluoride-hexafluoropropylene copolymer and polymethyl methacrylate in N-methylpyrrolidone, dispersed at 1800 r / min for 30 min, and then degassed under vacuum for 20 min. Subsequent drying, gel impregnation, and UV crosslinking steps were the same as in Example 1. The thickness of the gel solid electrolyte layer was 44 μm. The results showed a liquid separation rate of 2.9%, a mass loss rate of 6.8% at 60°C, and an ionic conductivity of 1.4 mS / cm at 25°C.

[0084] The positive electrode, negative electrode current collector, battery assembly steps, and initial formation process are consistent with those in Example 1.

[0085] Example 7 This embodiment discloses a self-generated negative electrode lithium metal solid-state battery. The difference compared to Embodiment 1 lies in the different content of oxide solid electrolyte filler in the low-electrolyte gel solid electrolyte layer, as detailed below.

[0086] In the low-precipitate gel solid electrolyte layer, the oxide solid electrolyte filler is Li7La3Zr2O. 12 D 50 The particle size is 450 nm. This filler accounts for 30% of the total mass of the low-precipitate gel solid electrolyte layer.

[0087] When preparing the polymer-supported film, Li7La3Zr2O 12The solution of polyvinylidene fluoride-hexafluoropropylene copolymer and polymethyl methacrylate in N-methylpyrrolidone was added in three portions. After each addition, the mixture was dispersed at 2000 rpm for 15 min. After all three additions, dispersion continued for 30 min, followed by vacuum degassing for 25 min. Subsequent drying, gel impregnation, and UV crosslinking procedures were the same as in Example 1. The thickness of the solid electrolyte layer was 50 μm. Tests showed a liquid separation rate of 1.5%, a mass loss rate of 4.2% at 60°C, and an ionic conductivity of 1.2 mS / cm at 25°C.

[0088] The positive electrode, negative electrode current collector, battery assembly steps, and initial formation process are consistent with those in Example 1.

[0089] Comparative Example 1 The only difference between this comparative example and Example 1 is that the Sn capacity calibration layer is not provided in the negative electrode current collector.

[0090] Specifically, after the copper foil substrate was ultrasonically cleaned and dried sequentially with acetone, anhydrous ethanol, and deionized water, a nitrogen-doped carbon layer was directly deposited on the surface of the copper foil substrate. The thickness of the nitrogen-doped carbon layer was 180 nm, and the sheet resistivity was 2.5 Ω / sq. The positive electrode, the low-electrolyte gel solid electrolyte layer, the battery assembly steps, and the initial formation process were all consistent with those in Example 1.

[0091] In this comparative example, the surface of the negative electrode current collector lacks an alloyable metal capacity calibration layer and does not have the theoretical lithium receiving capacity and alloyed receiving sites provided by the Sn capacity calibration layer.

[0092] Comparative Example 2 The only difference between this comparative example and Example 1 is that no carbon coating is provided in the negative electrode current collector.

[0093] Specifically, a Sn capacity calibration layer with a thickness of 700 nm is deposited on the surface of the copper foil substrate, with a unit area mass of 0.512 mg / cm³. 2 Q2 has a capacity of 0.508 mAh / cm³. 2 The surface of the Sn capacity calibration layer is no longer covered with a nitrogen-doped carbon layer. The positive electrode, the low-electrolyte gel solid electrolyte layer, the battery assembly steps, and the initial formation process are all consistent with those in Example 1.

[0094] In this comparative example, the surface of the negative electrode current collector has a Sn capacity calibration layer, but lacks a continuous carbon coating covering the Sn capacity calibration layer.

[0095] Comparative Example 3 The only difference between this comparative example and Example 1 is that the Sn capacity calibration layer thickness and the mass per unit area are significantly reduced.

[0096] Specifically, the Sn capacity calibration layer has a thickness of 118 nm and a mass per unit area of ​​0.086 mg / cm³.2 According to Li 4.4 Sn calculates Q2 to be 0.085 mAh / cm³. 2 The positive electrode Q1 has a capacity of 0.60 mAh / cm³. 2 The Q1 / Q2 ratio is 7.06. The nitrogen-doped carbon layer has a thickness of 180 nm and a sheet resistivity of 2.5 Ω / sq. The positive electrode, the low-electrolyte gel solid electrolyte layer, the battery assembly steps, and the initial formation process are all consistent with those in Example 1.

[0097] In this comparative example, the lithium receiving capacity of the Sn capacity calibration layer is significantly lower than that of Example 1, and the Q1 / Q2 ratio is significantly higher than that of Example 1.

[0098] Comparative Example 4 Compared with Example 1, the only difference in this comparative example is that the Sn capacity calibration layer thickness and the mass per unit area are significantly improved.

[0099] Specifically, the Sn capacity calibration layer has a thickness of 1815 nm and a mass per unit area of ​​1.328 mg / cm³. 2 According to Li 4.4 Sn calculates Q2 to be 1.318 mAh / cm³. 2 The positive electrode Q1 has a capacity of 0.60 mAh / cm³. 2 The Q1 / Q2 ratio is 0.46. The nitrogen-doped carbon layer has a thickness of 180 nm and a sheet resistivity of 2.5 Ω / sq. The positive electrode, the low-electrolyte gel solid electrolyte layer, the battery assembly steps, and the initial formation process are all consistent with those in Example 1.

[0100] In this comparative example, the lithium receiving capacity of the Sn capacity calibration layer is significantly higher than that of Example 1, and the Q1 / Q2 ratio is significantly lower than that of Example 1.

[0101] Comparative Example 5 The only difference between this comparative example and Example 1 is that the gel electrolyte layer is in a high-elution state by reducing the content of polymer backbone and crosslinking monomer.

[0102] Specifically, in preparing the polymer-supported membrane, the amount of polyvinylidene fluoride-hexafluoropropylene copolymer was reduced from 70 parts to 35 parts, the amount of polymethyl methacrylate was reduced from 20 parts to 10 parts, and the amount of N-methylpyrrolidone was maintained at 420 parts. (Li7La3Zr2O) 12 The filler comprises 15% of the total mass of the electrolyte layer. In the gel solution, dimethoxymethane comprises 85% of the total mass of the non-aqueous solvent, lithium bis(fluorosulfonyl)imide concentration is 2.5 mol / L, polyethylene glycol diacrylate comprises 1.0% of the lithium salt solution mass, and 2-hydroxy-2-methylphenylacetone comprises 1.0% of the polyethylene glycol diacrylate mass. The wetting and UV crosslinking steps are consistent with Example 1, and the gel layer thickness is 45 μm.

[0103] The gel electrolyte layer showed a separation rate of 8.5% after standing at 0.2 MPa for 30 min, a mass loss rate of 12.0% after standing at 60°C for 24 h, and an ionic conductivity of 2.3 mS / cm at 25°C. The positive electrode, negative electrode current collector, battery assembly steps, and initial formation regime were all consistent with those in Example 1.

[0104] In this comparative example, the ionic conductivity of the gel electrolyte layer is still at a high level, but the liquid separation rate and heat loss rate are significantly higher than those in Example 1.

[0105] Comparative Example 6 The only difference between this comparative example and Example 1 is that the highest voltage of the first formation is reduced, and the first high-voltage formation was not performed.

[0106] Specifically, the initial transformation steps are as follows: S1, Charge to 4.30V at 0.03C; S2, continue charging at 0.08C to 4.45V; S3. Charge at a constant voltage of 4.45V until the current drops to 0.02C; S4, discharge to 2.20V at 0.08C.

[0107] The upper limit voltage for subsequent cycles is 4.45V, and the discharge cutoff voltage is 2.20V. The positive electrode, negative current collector, low-electrolyte gel solid electrolyte layer, and battery assembly steps are all the same as in Example 1.

[0108] In this comparative example, the highest initial formation voltage is lower than that in Example 1, and it does not enter the initial high-voltage formation range of 4.55 to 4.70 V.

[0109] Comparative Example 7 The only difference between this comparative example and Example 1 is that the upper limit voltage in subsequent cycles continues to be converted to the highest voltage initially.

[0110] Specifically, the initial formation process is the same as in Example 1, with a maximum initial formation voltage of 4.65V. After the initial formation, the upper limit voltage for subsequent cycles is still set at 4.65V, and the discharge cutoff voltage is 2.20V. The positive electrode sheet, negative electrode current collector, low-electrolyte gel solid electrolyte layer, and battery assembly steps are all the same as in Example 1.

[0111] In this comparative example, the upper limit voltage of subsequent cycles was not lower than the highest voltage of the first formation, and no voltage distinction was made between the first formation stage and the subsequent cycle stage.

[0112] Comparative Example 8 The only difference between this comparative example and Example 1 is that the proportion of lithium-rich components in the positive electrode active material is significantly reduced, resulting in insufficient additional lithium release capacity per unit area of ​​the positive electrode sheet in the first cycle.

[0113] Specifically, the positive electrode active material is 0.1Li₂MnO₃·0.9LiNi 0.25 Co 0.1 Mn 0.6 Al 0.05 O2, D 50 The particle size is 8.3 μm. By mass percentage, the positive electrode active layer comprises 94.0% positive electrode active material, 3.0% conductive carbon black, and 3.0% polyvinylidene fluoride binder. The single-sided areal capacity of the positive electrode active layer is 4.2 mAh / cm². 2 Based on lithium-ion half-cell testing, the irreversible capacity (Q1) per unit area during the first cycle is 0.18 mAh / cm². 2 .

[0114] The negative electrode current collector, low-electrolyte gel solid electrolyte layer, battery assembly steps, and initial formation process were all consistent with those in Example 1. In this comparative example, Q2 was 0.508 mAh / cm³. 2 Q1 / Q2 is 0.35.

[0115] In this comparative example, the cathode still uses a lithium-rich manganese-based cathode material system, but the proportion of lithium-rich components is significantly reduced. The matching relationship between the additional lithium release capacity in the first cycle of the cathode and the theoretical lithium receiving capacity of the Sn capacity calibration layer is no longer formed as in Example 1.

[0116] Performance testing To verify the overall performance of the batteries obtained in the above embodiments and comparative examples, the self-generated negative electrode lithium metal solid batteries prepared in Examples 1 to 7 and Comparative Examples 1 to 8 were subjected to the following performance tests.

[0117] 1. First-cycle coulombic efficiency test. After the prepared pouch cells were left to stand at 25°C for 12 hours, the first charge and discharge cycles were performed according to the first formation regime corresponding to each embodiment and comparative example. The first formation charge capacity and the first formation discharge capacity were recorded, and the first-cycle coulombic efficiency was calculated based on the ratio of the first formation discharge capacity to the first formation charge capacity.

[0118] 2. Cycle Retention Test. After the initial formation, the batteries were subjected to constant current charge-discharge cycle tests at 25°C. The charge rate was 0.2C, the discharge rate was 0.2C, and the upper charge voltage and discharge cutoff voltage followed the subsequent cycle regimes corresponding to the respective embodiments and comparative examples. The discharge capacity at week 1 and week 100 were recorded, and the capacity retention rate after 100 weeks was calculated based on the ratio of the discharge capacity at week 1 to the discharge capacity at week 1.

[0119] 3. Rate Performance Testing. After the initial formation, the batteries were sequentially discharged at 0.1C, 0.2C, 0.5C, and 1.0C at 25°C, for three cycles at each rate. The discharge capacity at the third cycle was taken as the corresponding rate discharge capacity. The 1.0C capacity retention rate was calculated based on the 0.1C discharge capacity.

[0120] 4. Interface Impedance Test. Batteries after initial formation and after 100 cycles were adjusted to 50% state of charge and allowed to stand at 25°C for 4 hours before AC impedance testing. The test frequency range was 1MHz to 0.1Hz, and the disturbance voltage was 10mV. The interface impedance was obtained based on mid-to-high frequency semicircular fitting and used to evaluate the changes in the self-generated negative electrode interface before and after cycling.

[0121] The test results are shown in the table below.

[0122]

[0123] The test results show that the batteries prepared in Examples 1 to 7 exhibit higher first-cycle coulombic efficiency, higher 100-cycle capacity retention, better rate performance, and lower interfacial impedance growth. Compared with the comparative examples, the batteries in the examples are able to form a more stable self-generated negative electrode interface after the first formation and maintain better capacity output and interface stability during subsequent cycles.

[0124] Examples 1 to 3, using different positive electrode surface capacities and different Sn capacity calibration layer settings, all achieved good electrochemical performance. This indicates that when the additional lithium release capacity of the positive electrode in the first cycle matches the theoretical lithium receiving capacity of the alloyable metal capacity calibration layer, the active lithium released during the first formation process can participate well in the alloying and initial lithium deposition on the negative electrode side, thereby improving the battery's first-cycle efficiency and cycle retention capability.

[0125] Examples 4 and 5 use Sn-Mg composite metal layers and Zn capacity calibration layers, respectively. Their performance results are similar to those of Example 1, indicating that alloyable metal capacity calibration layers can be achieved through different alloyable metals or composite metal layers. As long as their theoretical lithium receiving capacity is compatible with the additional lithium release capacity of the positive electrode in the first cycle, they can provide an effective alloying receiving basis and a lithiophilic induction interface for the self-generation process of the negative electrode.

[0126] Examples 6 and 7 adjusted the type or content of oxide solid electrolyte filler, and the battery still maintained good cycle retention and interfacial impedance level, indicating that the low-electrolyte gel solid electrolyte layer can provide a stable ion transport environment and interfacial contact state for the negative electrode self-generation process within the limited composition and performance range.

[0127] Comparative Example 1 lacked an alloyable metal capacity calibration layer, and Comparative Example 2 lacked a carbon coating. Both exhibited lower first-cycle coulombic efficiency, cycle retention, and rate performance compared to Example 1, and showed a more significant increase in interfacial impedance after cycling. These results indicate that the alloyable metal capacity calibration layer and the carbon coating play crucial roles in anode-side alloying acceptance, lithiophilic nucleation, and electron transport homogenization, respectively. Their combined effect is more conducive to forming a stable, self-generated anode interface.

[0128] Comparative Examples 3 and 4 correspond to cases where the capacity calibration layer is too thin and too thick, respectively, and their performance is lower than that of Example 1. This result indicates that the lithium receiving capacity of the alloyable metal capacity calibration layer needs to be matched with the additional lithium release capacity of the positive electrode in the first cycle. Both excessively low and excessively high receiving capacities are detrimental to the stable progress of the initial negative electrode formation process.

[0129] Comparative Example 5, employing a high-leakage gel electrolyte layer, exhibited lower cycle retention and rate performance compared to Example 1, with a more significant increase in interfacial impedance. These results indicate that the gel solid electrolyte layer not only needs ion transport capabilities but also requires maintaining low leakage and a stable interfacial contact state to ensure a more balanced lithium-ion supply during the negative electrode self-generation process.

[0130] Comparative Example 6 did not undergo initial high-voltage formation, while Comparative Example 7 continued to use the highest initial formation voltage in subsequent cycles. Both examples exhibited lower cycle stability than Example 1. This result indicates that the combination of a high initial formation voltage and a lower upper limit voltage in subsequent cycles is beneficial for triggering additional lithium release from the lithium-rich manganese-based cathode material and completing the self-generation of the anode during the initial formation stage, while maintaining a relatively stable electrode interface in subsequent cycles.

[0131] In Comparative Example 8, the proportion of lithium-rich components in the positive electrode active material was significantly reduced, and the battery performance was significantly lower than that of Example 1. This result indicates that the additional active lithium provided by the lithium-rich manganese-based positive electrode material in the first cycle is an important lithium source basis for the self-generation process of the negative electrode. When the additional lithium release capacity on the positive electrode side is insufficient, even if the negative electrode current collector has a capacity calibration layer and a carbon coating, it is difficult to obtain the same self-generation negative electrode effect as in the Example.

[0132] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A self-generating negative electrode lithium metal solid-state battery, characterized in that, Includes positive electrode, negative electrode current collector, and low-electrolyte gel solid electrolyte layer; The positive electrode sheet includes a positive current collector and a positive active layer disposed on the surface of the positive current collector, wherein the positive active layer includes a lithium-rich manganese-based positive electrode material; The negative electrode current collector includes a copper foil substrate, an alloyable metal capacity calibration layer disposed on the surface of the copper foil substrate, and a carbon plating layer covering the alloyable metal capacity calibration layer. The low-precipitate gel solid electrolyte layer includes a cross-linked polymer network and DMM and LiFSI retained in the cross-linked polymer network; The additional lithium release capacity per unit area in the first cycle of the lithium-rich manganese-based cathode material is denoted as Q1, and the theoretical lithium receiving capacity per unit area of ​​the alloyable metal capacity calibration layer is denoted as Q2. The ratio of Q1 to Q2 is 1.15 to 1.

45. The highest initial formation voltage of the self-generated negative electrode lithium metal solid-state battery is 4.55–4.70V, and the upper limit voltage of subsequent cycles is 0.15–0.25V lower than the highest initial formation voltage. Wherein, Q1 is the first-cycle irreversible capacity per unit area obtained by charging the positive electrode to 4.60V at 0.05C and then discharging it to 2.00V at 0.05C in a lithium half-cell.

2. The self-generating negative electrode lithium metal solid-state battery according to claim 1, characterized in that, The general chemical formula of the lithium-rich manganese-based cathode material is xLi2MnO3·(1-x)LiMO2, where 0.25≤x≤0.55, and M includes at least two elements selected from Ni, Co, Mn, Al, Mg, and Ti. In the lithium-rich manganese-based cathode material, Mn accounts for 55% to 85% of the total molar amount of transition metal elements.

3. A self-generating negative electrode lithium metal solid-state battery according to claim 1, characterized in that, The positive electrode active layer comprises the following components in weight percentage: 90%–96% lithium-rich manganese-based positive electrode material, 1.5%–5% conductive agent, and 2.5%–5% binder; the single-sided areal capacity of the positive electrode active layer is 3.0–5.5 mAh / cm². 2 Q1 is 0.30~1.20mAh / cm³. 2 .

4. A self-generating negative electrode lithium metal solid-state battery according to claim 1, characterized in that, The alloyable metal capacity calibration layer includes one or more of Sn, Ag, Mg, and Zn; when the alloyable metal is Sn, the corresponding lithium alloy phase is determined according to Li. 4.4 Sn is calculated; when the alloyable metal is Ag, the corresponding lithium alloy phase is calculated as LiAg; when the alloyable metal is Zn, the corresponding lithium alloy phase is calculated as LiZn; when the alloyable metal is Mg, the corresponding lithium alloy phase is calculated as Li3Mg.

5. A self-generating negative electrode lithium metal solid-state battery according to claim 1, characterized in that, The thickness of the alloyable metal capacity calibration layer is 0.35–1.40 μm, and the unit area mass of the alloyable metal capacity calibration layer is 0.25–1.00 mg / cm³. 2 Q2 is 0.25~1.00mAh / cm³. 2 The carbon coating includes one of an amorphous carbon layer, a nitrogen-doped carbon layer, and a graphitized carbon layer. The thickness of the carbon coating is 50–300 nm, and the sheet resistivity of the carbon coating is 0.8–10 Ω / sq.

6. A self-generating negative electrode lithium metal solid-state battery according to claim 1, characterized in that, The low-leakage gel solid electrolyte layer has a leakage rate of no more than 3% after standing at 0.2 MPa pressure for 30 min, a mass loss rate of no more than 8% after standing at 60℃ for 24 h, and an ionic conductivity of 0.5–5.0 mS / cm at 25℃.

7. A self-generating negative electrode lithium metal solid-state battery according to claim 1, characterized in that, The cross-linked polymer network is formed from one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, polyacrylonitrile, and polymethyl methacrylate; DMM accounts for 70% to 95% of the total mass of non-aqueous solvent in the low-precipitate gel solid electrolyte layer, and the concentration of LiFSI in the low-precipitate gel solid electrolyte layer is 1.8 to 3.2 mol / L.

8. A self-generating negative electrode lithium metal solid-state battery according to claim 1, characterized in that, The low-precipitate gel solid electrolyte layer also includes an oxide solid electrolyte filler, which comprises Li7La3Zr2O. 12 Li 1.3 Al0.3Ti 1.7 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 One or more of (PO4)3 and Li3PO4 are used to coat alumina, and the oxide solid electrolyte filler accounts for 5% to 30% of the total mass of the low-precipitate gel solid electrolyte layer.

9. A self-generating negative electrode lithium metal solid-state battery according to claim 1, characterized in that, The initial formation of the self-generated negative electrode lithium metal solid-state battery includes the following steps: S1: Charge to 4.30-4.45V at 0.02C-0.05C; S2: Continue charging at 0.05C to 0.10C until 4.55 to 4.70V; S3: Charge at a constant voltage of 4.55 to 4.70V until the current drops to 0.01C to 0.05C; S4: Discharge to 2.00-2.50V at 0.05C-0.10C; The upper limit voltage for subsequent cycles is 4.30–4.50V.

10. The application of a self-generating negative electrode lithium metal solid-state battery as described in any one of claims 1 to 9 in a high-energy-density secondary battery, battery module, or battery pack.

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