Anode-free lithium battery with in-situ plasma nitrided negative current collector and preparation method thereof

Abstract

This invention discloses an in-situ plasma nitriding-treated negative electrode current collector and its preparation method, relating to the field of lithium battery technology. The battery comprises a positive electrode sheet, a separator, a liquid organic electrolyte, and an atmospheric pressure online plasma nitriding modified copper foil negative electrode current collector. The battery has a negative electrode-free structure; during assembly, the negative electrode region only has the atmospheric pressure online plasma nitriding modified copper foil negative electrode current collector, without any pre-placed negative electrode active material. The atmospheric pressure online plasma nitriding modified copper foil negative electrode current collector includes a copper foil substrate and a copper nitride nano-modified layer generated by online continuous plasma nitriding under atmospheric pressure. This invention utilizes the in-situ generated copper nitride nano-modified layer, which transforms into a lithium nitride-based interface layer during the first charge of the battery. This layer guides the uniform deposition and stripping of lithium ions, effectively suppressing the formation of lithium dendrites and dead lithium, thereby improving battery cycle life and safety.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to a negative electrode-free lithium battery with in-situ plasma nitriding treatment of the negative electrode current collector and its preparation method. Background Technology

[0002] Electrodeless lithium batteries use only copper foil as the current collector. They rely on the lithium source provided by the positive electrode to deposit metallic lithium in situ during the charging process to form the negative electrode. This can maximize the battery's energy density, simplify the structure, and reduce costs, making it the core technology route for the next generation of high-energy-density batteries.

[0003] Existing negative electrode-less batteries suffer from the following critical industry pain points: Copper foil has poor lithium affinity: the nucleation overpotential on the surface of pure copper is high, lithium deposition is uneven, and lithium dendrites are easily generated, causing short circuits, gas expansion, and poor safety.

[0004] SEI film is porous and fragile: Ordinary copper foil has high surface inertness, resulting in high impedance and poor stability of the formed SEI. During the cycle process, it continuously breaks and regenerates, leading to a rapid decay of coulombic efficiency.

[0005] Complex process and high pollution: Traditional wet coating of lithiophilic layer, pre-plating of lithium, and chemical doping process have solvent residue, many steps, cannot be continuously produced online, and high cost.

[0006] Modified layers are prone to peeling off: Offline modified copper foil is prone to secondary oxidation and contamination during the transfer, rolling and coating processes, resulting in a significant decrease in interface stability. Therefore, a negative electrode-free lithium battery with in-situ plasma nitriding treatment of the negative electrode current collector and its preparation method are proposed to solve this problem. Summary of the Invention

[0007] Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a negative electrode-free lithium battery with in-situ plasma nitriding treatment of the negative electrode current collector and its preparation method, thus solving the problems mentioned in the background art.

[0008] Technical solution To achieve the above objectives, the present invention is implemented through the following technical solution: an online in-situ nitrogen source plasma treatment of copper foil without a negative electrode, which is composed of a positive electrode sheet, a separator, a liquid organic electrolyte and an atmospheric pressure online plasma nitriding modified copper foil negative electrode current collector.

[0009] The main objective of this overall structure design is to address the problems of poor lithium affinity of copper current collectors, lithium dendrite growth, unstable solid electrolyte interface film, and the inability of existing modification processes to adapt to large-scale mass production in existing electrodeless lithium batteries. The goal is to build an electrodeless lithium battery system with stable interface, uniform lithium deposition, long cycle life, and continuous production capability, which can meet the application needs of consumer electronics, power batteries, energy storage power stations, and special small energy storage devices.

[0010] The atmospheric pressure online plasma nitriding modified copper foil negative electrode current collector includes a copper foil substrate and a copper nitride nano-modified layer generated by online continuous plasma nitriding under atmospheric pressure. The main purpose of this two-layer structure is to construct a lithium-friendly transition layer on the copper foil surface through in-situ modification under atmospheric pressure. During the first charge of the battery, it is converted into a stable lithium nitride interface layer in situ, solving the problem of poor compatibility between bare copper current collectors and lithium and electrolytes. At the same time, it avoids the defects of high cost, low production efficiency and inability to continuously produce using vacuum plasma processes.

[0011] Preferably, the copper foil substrate includes at least one of electrolytic copper foil, rolled copper foil, copper alloy ultrathin copper foil, foamed copper foil, porous copper foil, and non-woven copper-plated foil, with a thickness of 4μm to 12μm. Electrolytic copper foil has moderate surface roughness, suitable for conventional mass production processes; rolled copper foil has high density and good mechanical strength, suitable for high-rate charge and discharge requirements; copper alloy ultrathin copper foil has excellent oxidation resistance, suitable for long-term storage scenarios; foamed copper foil and porous copper foil have large specific surface area, which can reduce local current density, suitable for high-capacity batteries; non-woven copper-plated foil has good flexibility, suitable for flexible batteries. This thickness range can significantly reduce battery weight and volume while ensuring the mechanical strength and conductivity of the current collector, avoiding the problems of decreased energy density due to excessively thick copper foil, or easy breakage and wrinkling during processing due to excessively thin copper foil.

[0012] Preferably, the phase of the copper nitride nano-modified layer includes at least one of Cu3N and nitrogen-doped copper oxide, with a thickness of 5 nm to 30 nm. It has a dense and uniform structure, is chemically bonded in situ to the copper foil substrate, has an adhesion grade of at least 0, and is free of cracks and peeling. Both Cu3N and nitrogen-doped copper oxide possess excellent lithiophilic properties and can quantitatively generate lithium nitride through reaction with lithium. This thickness range ensures that the modified layer has sufficient lithiophilic sites and reactivity, while almost not increasing the weight and thickness of the copper foil, and almost not sacrificing the energy density of the battery. This avoids the problems of increased interfacial impedance due to an excessively thick modified layer, or insufficient modification and inadequate interfacial stability due to an excessively thin layer.

[0013] The positive electrode sheet is made by uniformly mixing positive electrode active material, conductive carbon black, and polyvinylidene fluoride binder in a mass ratio of 92:4:4, coating it onto the surface of an aluminum current collector for lithium batteries, drying it at 80℃ to 120℃, and rolling it to a compaction density of 2.8 g / cm³. 3 Up to 3.6 g / cm 3 It is manufactured. The main purpose of this component is to provide all the active lithium ions required for the battery's charge and discharge cycles, serving as the positive electrode reaction carrier and determining the battery's operating voltage and theoretical capacity.

[0014] Preferably, the positive electrode active material includes at least one or more composite systems selected from ternary NCM, NCA, lithium iron phosphate, lithium manganese oxide, and lithium-rich manganese-based materials. Ternary NCM and NCA have high energy density, making them suitable for consumer electronics and high-end power batteries; lithium iron phosphate has long cycle life and good safety, making it suitable for energy storage power stations and low-to-mid-range power batteries; lithium manganese oxide has low cost and good low-temperature performance, making it suitable for low-end consumer electronics and low-temperature applications; lithium-rich manganese-based materials have high specific capacity, making them suitable for next-generation high-energy-density batteries. Composite systems can combine the advantages of different positive electrode materials to achieve comprehensive optimization of battery performance.

[0015] The separator is a microporous separator used in lithium batteries. The main purpose of this component is to physically isolate the positive and negative electrodes, preventing short circuits caused by direct contact between them, while allowing lithium ions to pass freely and blocking electron transport to ensure the normal electrochemical reaction of the battery.

[0016] Preferably, the separator includes at least one of polypropylene-based microporous separator, polyethylene-based microporous separator, and ceramic-coated modified composite separator. Polypropylene-based microporous separator has good chemical stability and low cost; polyethylene-based microporous separator has low pore-closing temperature and good safety performance; ceramic-coated modified composite separator has high mechanical strength and excellent high-temperature resistance, making it suitable for batteries with high energy density and high safety requirements.

[0017] The liquid organic electrolyte is a carbonate-based lithium hexafluorophosphate electrolyte containing fluoroethylene carbonate additives, but does not contain flame retardants or high-concentration salt-modifying components. The main purpose of this component is to act as a medium for lithium ion transport between the positive and negative electrodes, ensuring rapid lithium ion migration and smooth electrochemical reactions.

[0018] Preferably, the carbonate system solvent is a mixture of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:1:1; the concentration of lithium hexafluorophosphate is 1 mol / L; and the amount of fluoroethylene carbonate added is 5% to 10% of the total mass of the electrolyte. This solvent system has suitable dielectric constant and viscosity, ensuring sufficient dissolution of lithium salt and rapid migration of lithium ions; the 1 mol / L lithium hexafluorophosphate concentration is a conventional concentration for lithium batteries, balancing ionic conductivity and low-temperature performance; the fluoroethylene carbonate helps form a stable interface layer, further improving battery cycle performance. This invention eliminates the need for flame retardants and high-concentration salts, reducing electrolyte costs and avoiding the problems of increased electrolyte viscosity and decreased ionic conductivity caused by high-concentration salts.

[0019] During the first charge of the battery, lithium ions released from the positive electrode are deposited in situ on the surface of the atmospheric pressure online plasma nitride modified copper foil negative electrode current collector to form a metallic lithium negative electrode. The copper nitride nano-modified layer reacts electrochemically with the in-situ deposited lithium to generate a lithium nitride interface layer. The reaction formula is Cu3N+3Li→3Cu+Li3N. The lithium nitride interface layer acts as an artificial stable solid electrolyte interface framework to guide the uniform deposition of lithium ions and inhibit the formation of lithium dendrites and dead lithium.

[0020] This invention also provides a method for preparing a negative electrode-free lithium battery using online in-situ nitrogen source plasma treatment of copper foil, which includes the following steps: Step one involves unwinding the copper foil substrate and then sequentially using atmospheric pressure plasma physical cleaning to remove surface oil, dust, and oxide impurities, eliminating the need for any wet cleaning process. The main purpose of this step is to utilize the high-energy bombardment of plasma to simultaneously complete the entire pretreatment of the copper foil surface, replacing the traditional three-step wet cleaning process of acetone, ethanol, and deionized water. This achieves fully dry production, with no wastewater or solvent residue, while avoiding problems such as copper foil oxidation and solvent residue associated with wet processes.

[0021] Step two involves directly feeding the cleaned copper foil into a roll-to-roll atmospheric pressure online plasma treatment device. High-purity nitrogen-containing process gas is introduced, and an RF or DC glow discharge plasma power supply is activated. Under atmospheric pressure and a low temperature not exceeding 80°C, continuous plasma nitriding bombardment is performed on the copper foil surface, generating a copper nitride nano-modified layer in situ. Steps one and two are continuously completed in different chambers of the same roll-to-roll atmospheric pressure online plasma treatment device, eliminating the need for transfer. The main purpose of this step is to achieve continuous roll-to-roll nitriding modification of copper foil using atmospheric pressure plasma technology, solving the common industry problem of continuous production limitations in vacuum plasma processes. Simultaneously, the low-temperature treatment avoids copper foil deformation and oxidation, ensuring product yield.

[0022] Preferably, the high-purity nitrogen-containing process gas includes at least one of the following: a single high-purity nitrogen source, a nitrogen-argon mixture source, or a nitrogen-hydrogen mixture source; the plasma processing power is 500W to 2000W, the processing temperature is not higher than 80℃, and the copper foil conveyor speed is 5m / min to 15m / min. Using a single high-purity nitrogen source can significantly reduce raw material costs and safety risks; the nitrogen-argon mixture source can improve plasma stability and generate a more uniform modified layer; the nitrogen-hydrogen mixture source can simultaneously reduce copper oxide on the copper foil surface to copper metal, achieving better conductivity and nitriding modification effects on the copper foil surface. This range of power, temperature, and conveyor speed allows for precise control of the copper nitride modified layer thickness, ensuring that the structure and performance of the modified layer meet requirements. It is also compatible with existing high-speed continuous production lines in the lithium battery industry, operating at speeds of 5m to 15m per minute, avoiding copper foil damage due to excessive power or insufficient nitriding due to insufficient power.

[0023] Preferably, plasma treatment simultaneously performs physical cleaning, oxide layer removal, and nano-roughening of the copper foil surface, forming a uniform nano-uneven structure and increasing lithium nucleation sites. This integrated treatment method simplifies the production process, reduces equipment investment, and the nano-roughened structure further reduces the lithium nucleation overpotential and improves the uniformity of lithium deposition.

[0024] Step three: The modified copper foil is directly fed into the battery assembly process online via a continuous conveyor line, without secondary exposure or contamination. In a low-dew-point drying chamber, it is stacked or wound in the order of positive electrode sheet, separator, and modified copper foil negative electrode current collector. After injecting liquid organic electrolyte, it is sealed and allowed to stand to allow for full electrolyte wetting. The main purpose of this step is to achieve integrated continuous production of modification and assembly, avoiding secondary oxidation and contamination of the copper foil during transfer and storage in offline modification processes, and ensuring the interfacial stability of the modified layer.

[0025] Preferably, the dew point of the low-dew-point drying chamber is no higher than -40°C; the soaking time after electrolyte injection is 12 to 24 hours. These environmental conditions prevent moisture and oxygen from entering the battery, thus preventing electrolyte decomposition and electrode material oxidation. The stacking process is suitable for both pouch cells and large-size prismatic cells, while the winding process is suitable for both cylindrical cells and small-size prismatic cells, allowing for flexible selection based on battery type and manufacturing process. This soaking time ensures that the electrolyte fully wets all pores of the electrodes and separator, avoiding problems such as increased internal resistance and decreased utilization of active materials due to insufficient wetting.

[0026] Step four involves performing an initial low-rate constant current charge on the assembled battery cell. This allows the copper nitride nano-modified layer to undergo an electrochemical reaction with the in-situ deposited lithium, generating a lithium nitride interface layer. This completes the preparation and activation of the electrodeless lithium battery. The main purpose of this step is to achieve the in-situ conversion of copper nitride to lithium nitride, construct a stable artificial solid electrolyte interface layer, and simultaneously complete the initial activation of the battery, bringing it into normal operating condition.

[0027] Preferably, the initial low-rate constant current charge is 0.05C to 0.2C, charging to the rated operating cutoff voltage of the corresponding cathode material. Low-rate charging ensures the reaction between copper nitride and lithium proceeds fully, generating a uniform and dense lithium nitride interface layer, avoiding the problems of uneven reaction and interface layer defects caused by high-rate charging. Different cathode materials have different rated operating cutoff voltages: lithium manganese oxide is 4.2V, ternary NCM and NCA are 4.2V to 4.3V, lithium iron phosphate is 3.65V, and lithium-rich manganese-based cathodes are 4.5V to 4.6V. The appropriate charging cutoff voltage must be selected according to the type of cathode material to ensure battery safety and performance.

[0028] This invention constructs a copper nitride nano-modified layer on the surface of copper foil using an atmospheric pressure online continuous plasma nitriding process. During the first charge of the battery, this layer is in situ converted into a lithium nitride artificial interface layer, forming a complete and stable interface system and a mass production process. The copper nitride modified layer is chemically bonded to the copper foil substrate in situ, exhibiting strong adhesion and not detaching during cycling. The lithium nitride interface layer possesses high lithium-ion conductivity, strong lithiophilicity, and excellent chemical stability, significantly reducing the lithium nucleation overpotential, guiding uniform lithium-ion deposition and stripping, and avoiding localized current density concentrations. Meanwhile, the lithium nitride interface layer isolates the copper current collector from direct contact with the electrolyte, preventing continuous decomposition of the electrolyte on the copper foil surface and repeated rupture and reconstruction of the solid electrolyte interface film. The atmospheric pressure online process enables continuous roll-to-roll processing of copper foil, significantly improving production efficiency and reducing equipment costs. It is compatible with existing lithium battery mass production lines without requiring large-scale production line modifications. The various components work together to fundamentally suppress the formation of lithium dendrites and dead lithium, reducing the consumption of electrolyte and active lithium. Simultaneously, it solves the main bottleneck preventing mass production in existing modification processes, achieving a harmonious balance between high performance and mass production feasibility, making it suitable for large-scale industrial application.

[0029] Beneficial effects The present invention has the following beneficial effects: (1) The in-situ plasma nitriding treatment of negative electrode current collector and its preparation method, through the in-situ generated copper nitride nano-modified layer, is transformed into a lithium nitride-based interface layer during the first charge of the battery, which can guide the uniform deposition and stripping of lithium ions, effectively suppress the generation of lithium dendrites and dead lithium, and improve the cycle life and safety performance of the battery.

[0030] (2) The in-situ plasma nitriding treatment of the negative electrode current collector and its preparation method have a high ionic conductivity and good chemical stability of the lithium nitriding-based solid electrolyte interface layer. It is not easy to break and reconstruct during cycling, which can reduce the consumption of electrolyte and active lithium and improve the coulombic efficiency of the battery.

[0031] (3) The electrodeless lithium battery with in-situ plasma nitriding treatment of the negative electrode current collector and its preparation method. The prepared electrodeless lithium battery has stable coulombic efficiency and can maintain an average coulombic efficiency of over 99.5% over long-term cycling, with a slow capacity decay rate.

[0032] (4) The negative electrode-free lithium battery with in-situ plasma nitriding treatment of negative electrode current collector and its preparation method adopts atmospheric pressure online continuous plasma process, dry production throughout the process, no wastewater and no solvent residue, simple production process, low production cost, can realize continuous roll-to-roll processing of copper foil, and is fully compatible with existing lithium battery mass production lines.

[0033] (5) The present invention relates to a negative electrode-free lithium battery with an in-situ plasma nitriding treatment of the negative electrode current collector and its preparation method. The copper nitride nano-modified layer of the present invention is chemically bonded to the copper foil substrate in situ, with strong interfacial bonding force and is not easy to fall off during cycling. It also has good resistance to rolling and bending, and is suitable for subsequent processing steps in battery production.

[0034] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0035] Figure 1 This is a flowchart of a method for preparing a negative electrode-free lithium battery using an in-situ plasma nitriding treatment of the negative electrode current collector, according to the present invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment provides a cathode-free lithium battery and its preparation method based on online in-situ nitrogen source plasma treatment of copper foil. The cathode-free lithium battery consists of an atmospheric pressure online plasma nitriding modified copper foil cathode current collector, a positive electrode, a separator, and a liquid organic electrolyte.

[0039] The atmospheric pressure online plasma nitriding modified copper foil negative electrode current collector includes a 4μm electrolytic copper foil substrate and a 5nm copper nitride nano-modification layer generated by continuous online plasma nitriding at atmospheric pressure on its surface. The atmospheric pressure plasma nitriding process uses a single high-purity nitrogen gas source, an RF power of 500W, a processing temperature not exceeding 80℃, and a copper foil conveying speed of 15m / min. The positive electrode sheet is made by uniformly mixing lithium manganese oxide positive electrode active material, conductive carbon black, and polyvinylidene fluoride binder in a mass ratio of 92:4:4, coating it onto the surface of an aluminum current collector for lithium batteries, drying it at 80℃, and rolling it to a compaction density of 2.8g / cm³. 3 The separator is a polypropylene-based microporous membrane. The liquid organic electrolyte is a carbonate-based lithium hexafluorophosphate electrolyte containing fluoroethylene carbonate additives, with the fluoroethylene carbonate additive amounting to 5% of the total electrolyte mass. A 0.5Ah soft-pack negative electrode-free battery was prepared.

[0040] A method for preparing a negative electrode-free lithium battery using copper foil treated with in-situ nitrogen plasma includes the following steps: Step 1: After unwinding a 4μm electrolytic copper foil, it is fed into the cleaning chamber of a roll-to-roll atmospheric pressure in-line plasma treatment device. Atmospheric pressure plasma physical cleaning is used to remove surface oil, dust, and oxide impurities, eliminating the need for any wet cleaning process. Step 2: The cleaned copper foil is directly introduced into the nitriding chamber of the same device. High-purity nitrogen is introduced, and the radio frequency glow discharge plasma power supply is turned on. The foil is continuously processed at a speed of 15 m / min at a temperature not exceeding 80°C, generating a 5nm copper nitride nano-modified layer in situ on the copper foil surface. Step 3: The modified copper foil is directly fed into the battery assembly process via a continuous conveyor line. In a drying room with a dew point not exceeding -40°C, the foil is stacked and assembled in the order of positive electrode sheet - separator - modified copper foil negative electrode current collector. After injecting liquid organic electrolyte, the assembly is sealed and left to stand for 12 hours to allow the electrolyte to fully impregnate the foil. Step four: Charge the assembled battery cells at a low rate of 0.05C to 4.2V to complete battery preparation and activation.

[0041] Example 2

[0042] This embodiment provides a cathode-free lithium battery and its preparation method based on online in-situ nitrogen source plasma treatment of copper foil. The cathode-free lithium battery consists of an atmospheric pressure online plasma nitriding modified copper foil cathode current collector, a positive electrode, a separator, and a liquid organic electrolyte.

[0043] The atmospheric pressure online plasma nitriding modified copper foil negative electrode current collector includes a 12μm rolled copper foil substrate and a 30nm copper nitride nano-modification layer generated by atmospheric pressure online continuous plasma nitriding on its surface. The atmospheric pressure plasma nitriding process uses a nitrogen and hydrogen mixed gas source with a mixing volume ratio of 9:1, a DC power of 2000W, a processing temperature not exceeding 80℃, and a copper foil conveying speed of 5m / min. The positive electrode sheet is made by uniformly mixing lithium iron phosphate positive electrode active material, conductive carbon black, and polyvinylidene fluoride binder in a mass ratio of 92:4:4, coating it onto the surface of an aluminum current collector for lithium batteries, drying it at 120℃, and rolling it to a compaction density of 3.6g / cm³. 3 The separator is a ceramic-coated modified composite separator. The liquid organic electrolyte is a carbonate-based lithium hexafluorophosphate electrolyte containing fluoroethylene carbonate additives, with the fluoroethylene carbonate additive amounting to 10% of the total electrolyte mass. A 5Ah square negative electrode-free battery was prepared.

[0044] A method for preparing a negative electrode-free lithium battery using copper foil treated with in-situ nitrogen plasma includes the following steps: Step 1: After unwinding a 12μm rolled copper foil, it is fed into the cleaning chamber of a roll-to-roll atmospheric pressure in-line plasma treatment equipment. Atmospheric pressure plasma physical cleaning is used to remove surface oil, dust, and oxide impurities, eliminating the need for any wet cleaning process. Step 2: The cleaned copper foil is directly introduced into the nitriding chamber of the same equipment. A mixture of nitrogen and hydrogen gas is introduced, and a DC glow discharge plasma power supply is turned on. The foil is continuously processed at a speed of 5 m / min at a temperature not exceeding 80°C, generating a 30nm copper nitride nano-modified layer in situ on the copper foil surface. Step 3: The modified copper foil is directly fed into the battery assembly process via a continuous conveyor line. In a drying room with a dew point not exceeding -40°C, the foil is wound and assembled in the order of positive electrode sheet - separator - modified copper foil negative electrode current collector. After injecting liquid organic electrolyte, the assembly is sealed and left to stand for 24 hours to allow the electrolyte to fully impregnate the foil. Step four: Charge the assembled battery cells at a low rate of 0.2C to 3.65V to complete battery preparation and activation.

[0045] Example 3

[0046] This embodiment provides a negative electrode-free lithium battery based on plasma-treated copper foil and its preparation method, serving as a performance reference under ideal laboratory conditions. The negative electrode-free lithium battery consists of a vacuum plasma nitrided modified copper foil negative electrode current collector, a positive electrode sheet, a separator, and a liquid organic electrolyte.

[0047] The vacuum plasma nitriding modified copper foil negative electrode current collector includes a 4μm electrolytic copper foil substrate and a 5nm copper nitride nano-modification layer generated by vacuum plasma nitriding on its surface. The vacuum plasma nitriding process uses a single high-purity nitrogen gas source, a chamber vacuum degree of 1Pa, a radio frequency power of 50W, a processing temperature of 25℃, and a processing time of 5min. The composition, dosage, and preparation method of the positive electrode, separator, and liquid organic electrolyte are completely consistent with those in Example 1. A 0.5Ah soft-pack negative electrode-free battery was prepared.

[0048] The preparation method of a negative electrode-free lithium battery using plasma-treated copper foil includes the following steps: Step 1: Cut 4μm electrolytic copper foil to a specified size, and ultrasonically clean it sequentially with acetone, anhydrous ethanol, and deionized water for 10 min each to remove surface oil, dust, and oxidation impurities. Then, vacuum dry it at 80℃ for 2 h to obtain a clean copper foil substrate. Step 2: Place the clean copper foil substrate into a vacuum plasma treatment chamber, evacuate to 1 Pa, introduce high-purity nitrogen gas, turn on the radio frequency glow discharge plasma power supply, and treat it at 25℃ for 5 min. After cooling, remove it to obtain a negative electrode current collector with a 5nm copper nitride nano-modified layer on the surface. Step 3: In a drying room with a dew point not higher than -40℃, stack and assemble the positive electrode sheet, separator, and modified copper foil negative electrode current collector in that order. Inject liquid organic electrolyte, seal the assembly, and let it stand for 12 h to allow the electrolyte to fully impregnate the electrode. Step four: Charge the assembled battery cells at a low rate of 0.05C to 4.2V to complete battery preparation and activation.

[0049] Comparative Example 1 This comparative example provides a negative electrode-free lithium battery, whose composition and preparation method are basically the same as those in Example 1. The core difference is that the copper foil is not subjected to any plasma nitriding modification treatment, while the other components, dosages, and process parameters are completely consistent with those in Example 1.

[0050] Comparative Example 2 This comparative example provides a negative electrode-free lithium battery, whose composition and preparation method are basically the same as those in Example 1. The core difference is that a 15nm lithium nitride coating is coated on the surface of a 4μm ordinary electrolytic copper foil using magnetron sputtering. The remaining components, amounts, and process parameters are completely consistent with those in Example 1.

[0051] Experiment Example 1: Battery Cycle Performance Test The main purpose of this test is to verify the cycling performance advantages of the technical solution of this invention, and to compare the performance differences between the ideal state in the laboratory and the actual state in mass production.

[0052] Test items: Battery cycle life test, executed according to standard GB / T31484-2015, test indicators are first-cycle coulombic efficiency and capacity retention rate after different cycles; The surface morphology of the negative electrode was observed using a scanning electron microscope to examine the lithium deposition state on the surface of the negative electrode current collector after cycling.

[0053] The test samples were battery samples prepared in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2. The test conditions were room temperature (25°C) and a charge / discharge voltage range of 2.5V to 4.2V (applicable to Examples 1, 3, 1, and 2); and 2.0V to 3.65V (applicable to Example 2). The charge / discharge rate was 1C. The test results are shown in the table below: Examples 1, 3, Comparative Example 1, and Comparative Example 2 used a lithium manganese oxide cathode system, and the test ended at 500 cycles; Example 2 used a lithium iron phosphate cathode system, and the test continued to 800 cycles.

[0054] Analysis of Test Results: The electrochemical performance of Examples 1 and 3 is basically the same, proving that the atmospheric pressure online process can achieve the same modification effect as the vacuum process. The first-cycle coulombic efficiency and cycle capacity retention of Examples 1 and 2 are higher than those of Comparative Examples 1 and 2. Comparative Example 1 uses unmodified copper foil, and during cycling, lithium deposition is uneven, with a large number of lithium dendrites and dead lithium forming, leading to rapid capacity decay. Comparative Example 2 uses a lithium nitride coating applied by magnetron sputtering, and the coating peels off during cycling, with lithium dendrites growing in the peeled areas, resulting in performance degradation. The lithium deposition on the surface of the negative electrode current collector in Examples 1 and 2 is smooth, with no obvious lithium dendrites or dead lithium, verifying the guiding effect of the atmospheric pressure online plasma nitride modification layer on lithium deposition.

[0055] Experiment Example 2: Battery Interface Impedance Test The main purpose of this test was to verify the improvement effect of the technical solution of this invention on the stability of the electrode interface, and to compare the interface performance differences between the ideal laboratory conditions and the actual mass production conditions. The test items are as follows: AC impedance test, performed according to standard GB / T31486-2015, the test indicators are initial interface impedance, interface impedance after 100 cycles, and impedance growth rate.

[0056] The test samples were battery samples prepared in Examples 1, 2, and 3, Comparative Example 1, and Comparative Example 2. The test conditions were room temperature (25°C) and the test frequency range was 10 Hz. -2 Hz to 10 5 The test results are shown in the table below: Hz, amplitude 5mV: Analysis of Test Results: The interfacial impedance data of Examples 1 and 3 are completely consistent, proving that the atmospheric pressure online process can construct an electrode interface as stable as the vacuum process. The initial interfacial impedances of Examples 1 and 2 are lower than those of Comparative Examples 1 and 2, and the impedance growth rate after 100 cycles is significantly lower. The interfacial impedance of Comparative Example 1 increases rapidly with cycling, due to the repeated rupture and reconstruction of the solid electrolyte interfacial film. The interfacial impedance growth rate of Comparative Example 2 is higher than that of the two examples, due to the instability of the interface caused by coating peeling. Example 2 has better interfacial stability than Example 1 due to its denser modified layer and stronger adhesion, further verifying the regulatory effect of atmospheric pressure online plasma nitriding modification process parameters on interfacial performance.

[0057] Example 3 illustrates a vacuum process under ideal laboratory conditions. Its electrochemical performance is comparable to the atmospheric pressure online process. However, the vacuum process suffers from high equipment costs, low production efficiency, and inability to achieve continuous production, making it only suitable for small-batch sample preparation in the laboratory. Examples 1 and 2 represent atmospheric pressure online processes under realistic mass production conditions. While maintaining the same electrochemical performance as the vacuum process, they achieve continuous roll-to-roll processing of copper foil, significantly improving production efficiency and reducing equipment costs. They are fully compatible with existing lithium battery mass production lines and are suitable technical solutions for large-scale industrial applications.

[0058] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0059] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A negative electrode-free lithium battery using online in-situ nitrogen source plasma treatment of copper foil, characterized in that, It consists of a positive electrode plate, a separator, a liquid organic electrolyte, and an atmospheric pressure online plasma nitrided modified copper foil negative electrode current collector; The battery has a negative electrode-free structure. During assembly, only an atmospheric pressure online plasma nitriding modified copper foil negative electrode current collector is set in the negative electrode area, and no negative electrode active material is pre-placed. The atmospheric pressure online plasma nitriding modified copper foil negative electrode current collector includes a copper foil substrate and a copper nitride nano-modified layer generated by online continuous plasma nitriding under atmospheric pressure. The positive electrode provides a carrier for active lithium ions; the separator is a medium that physically isolates the positive and negative electrodes and allows lithium ion transport. Liquid organic electrolytes serve as channels for lithium ion transport between the positive and negative electrodes; During the first charge of the battery, lithium ions released from the positive electrode are deposited in situ on the surface of the negative electrode current collector modified by plasma nitride at atmospheric pressure to form a metallic lithium negative electrode. The copper nitride nano-modified layer reacts electrochemically with the in-situ deposited lithium to generate a lithium nitride interface layer. The lithium nitride interface layer acts as an artificial stable solid electrolyte interface framework to guide the uniform deposition of lithium ions and inhibit the formation of lithium dendrites and dead lithium.

2. The negative electrode-free lithium battery with online in-situ nitrogen source plasma treatment of copper foil according to claim 1, characterized in that, The copper foil substrate includes at least one of electrolytic copper foil, rolled copper foil, copper alloy ultrathin copper foil, foamed copper foil, porous copper foil, and non-woven copper-plated foil, with a thickness of 4μm to 12μm.

3. The negative electrode-free lithium battery with online in-situ nitrogen source plasma treatment of copper foil according to claim 1, characterized in that, The phase of the copper nitride nano-modified layer includes at least one of Cu3N and nitrogen-doped copper oxide, with a thickness of 5nm to 30nm, a dense and uniform structure, in-situ chemical bonding with the copper foil substrate, an adhesion of not less than grade 0, and no cracks or peeling.

4. The negative electrode-free lithium battery with online in-situ nitrogen source plasma treatment of copper foil according to claim 1, characterized in that, The positive electrode sheet is made by coating a positive electrode active material onto an aluminum current collector. The positive electrode active material includes at least one or more composite systems of ternary NCM, NCA, lithium iron phosphate, lithium manganese oxide, and lithium-rich manganese-based materials.

5. The negative electrode-free lithium battery with online in-situ nitrogen source plasma treatment of copper foil according to claim 1, characterized in that, The separator includes at least one of polypropylene-based microporous separator, polyethylene-based microporous separator, and ceramic-coated modified composite separator; the liquid organic electrolyte is a carbonate-based lithium hexafluorophosphate electrolyte containing fluoroethylene carbonate additives, but does not contain flame retardants or high-concentration salt-modified components.

6. A method for preparing a negative electrode-free lithium battery by online in-situ nitrogen source plasma treatment of copper foil, characterized in that, The preparation of the electrodeless lithium battery for online in-situ nitrogen source plasma treatment of copper foil according to claim 1 includes the following steps: Step 1: After unwinding the copper foil substrate, use plasma physical cleaning to remove surface oil, dust and oxidation impurities; Step 2: The cleaned copper foil is sent into the atmospheric pressure online plasma treatment equipment, high-purity nitrogen-containing process gas is introduced, the glow discharge plasma power supply is turned on, and the copper foil surface is subjected to continuous plasma nitriding bombardment treatment under atmospheric pressure and low temperature conditions not exceeding 80°C, so as to generate copper nitride nano-modified layer in situ on the copper foil surface. Step 3: The modified copper foil is sent to the battery assembly process. In a low dew point drying room environment, it is assembled in the order of positive electrode sheet, separator to modified copper foil negative electrode current collector. The assembly methods include stacking and winding. After injecting liquid organic electrolyte, it is sealed and left to stand to allow the electrolyte to fully wet it. Step four involves performing a first low-rate constant current charge on the assembled battery cell to allow the copper nitride nano-modified layer to undergo an electrochemical reaction with the in-situ deposited lithium to generate a lithium nitride interface layer, thus completing the preparation and activation of the negative electrode-free lithium battery.

7. The method for preparing a negative electrode-free lithium battery by online in-situ nitrogen source plasma treatment of copper foil according to claim 6, characterized in that, In step two, the high-purity nitrogen-containing process gas includes at least one of the following: a single source of high-purity nitrogen, a mixed source of nitrogen and argon, or a mixed source of nitrogen and hydrogen; the plasma processing power is 500W to 2000W, the processing temperature is not higher than 80℃, and the copper foil conveying speed is 5m / min to 15m / min.

8. The method for preparing a negative electrode-free lithium battery by online in-situ nitrogen source plasma treatment of copper foil according to claim 6, characterized in that, In step two, plasma treatment simultaneously completes the physical cleaning, oxide layer removal, and nano-roughening of the copper foil surface, forming a uniform nano-uneven structure and increasing lithium nucleation sites.

9. The method for preparing a negative electrode-free lithium battery by online in-situ nitrogen source plasma treatment of copper foil according to claim 6, characterized in that, In step three, the dew point of the low dew point drying room is not higher than -40℃; the soaking time after liquid injection is 12h to 24h.

10. The method for preparing a negative electrode-free lithium battery by online in-situ nitrogen source plasma treatment of copper foil according to claim 6, characterized in that, In step four, the initial low-rate constant current charging rate is 0.05C to 0.2C, charging to the rated operating cutoff voltage of the corresponding positive electrode material.

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