A long-life, high-output-power bipolar all-solid-state battery

Abstract

This invention relates to the field of battery technology and discloses a long-life, high-output-power bipolar all-solid-state battery, comprising at least one single-cell stacked structure, consisting sequentially of a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer. The average thickness of the negative electrode active material layer is controlled between 4.0 μm and 6.0 μm. The battery is formed into a dense whole by hot-pressing the stacked structure under a pressure of 500 MPa to 650 MPa. This method employs a shared current collector with a Li-P-S-O amorphous sulfide interfacial resistance reducing layer and utilizes radio frequency magnetron sputtering to deposit a dense, ultra-thin solid electrolyte layer. By optimizing electrode dimensions and manufacturing processes, this invention overcomes the volume expansion effect and interfacial contact challenges of silicon-based negative electrodes, reduces the rate of increase in interfacial impedance and internal resistance, and achieves high capacity retention and excellent low-temperature, high-power output performance during long-cycle operation.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a long-life, high-output-power bipolar all-solid-state battery. Background Technology

[0002] With the increasing demands for range from electric vehicles and portable energy storage devices, all-solid-state lithium batteries, characterized by high energy density and high safety, have become a current research hotspot. Among them, bipolar all-solid-state batteries connect multiple single-cell units directly in series within the battery pack by sharing a current collector. This not only significantly reduces the mass and volume of inactive components such as connectors but also lowers the system's internal resistance, making it an ideal configuration for achieving lightweight and high-voltage battery modules.

[0003] However, the electrochemical performance of all-solid-state batteries is primarily limited by the interfacial contact state between the electrode materials and the solid electrolyte. Especially in silicon-based anode systems employing high theoretical specific capacity, the active material undergoes significant volume expansion and contraction during charge-discharge cycles. Unlike liquid electrolytes, which maintain wetted contact with electrode deformation, solid electrolytes lack a flow compensation mechanism with the active material particles. Frequent volume changes easily lead to stress concentration at the interface, causing particle breakage or interfacial delamination. This failure of physical contact disrupts ion transport channels, resulting in a sharp increase in interfacial impedance and rapid capacity decay.

[0004] Furthermore, the structural parameters and fabrication process of the electrode layer have a decisive impact on the power output characteristics of the battery. In current technological attempts, in pursuit of high energy density, there is often a tendency to increase the thickness of the electrode layer. However, in an all-solid-state system, this prolongs the solid-phase diffusion path of lithium ions, increases the tortuosity of ion transport, and leads to severe polarization under high current or low-temperature conditions. Conversely, if the electrode layer thickness is blindly reduced, the precision of the existing coating process and the uniformity of the conductive agent distribution can easily lead to discontinuities in the internal conductive network of the electrode, forming local electron islands, which actually increases the DC internal resistance. At the same time, conventional hot-pressing processes often fail to fully utilize the plastic deformation characteristics of sulfide electrolytes, making it difficult to form a mechanical interlocking structure between the active material and the electrolyte that is sufficient to resist long-term volume deformation, making it difficult for the battery to achieve both long cycle life and high power output performance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a long-life, high-output-power bipolar all-solid-state battery. This solves the problems of existing all-solid-state batteries, especially those using silicon-based anodes, where the volume expansion and contraction of the active material during charging and discharging leads to increased internal resistance and reduced cycle life. Furthermore, increasing electrode thickness to pursue energy density often results in decreased ion transport kinetics, making it difficult to balance high output power and long cycle life.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a long-life, high-output-power bipolar all-solid-state battery, comprising at least one single-cell stacked structure, wherein the single-cell stacked structure sequentially comprises a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer in spatial structure; the average thickness of the negative electrode active material layer is 4.0 μm-6.0 μm; the bipolar all-solid-state battery is a dense, integral structure formed by hot-pressing the single-cell stacked structure under a pressure of 500 MPa-650 MPa; the weight ratio of the negative electrode active material, sulfide solid electrolyte, and conductive agent in the negative electrode active material layer is 65:30:5; the weight ratio of the positive electrode active material, sulfide solid electrolyte, and conductive agent in the positive electrode active material layer is 70:25:5.

[0007] By adopting the above technical solution, due to the use of the aforementioned thickness of the negative electrode active material layer, the high-pressure hot-pressing process, and the optimized component combination, the beneficial effects of stable interface contact, high ion transport efficiency, and long cycle life are achieved. The specific mechanism is as follows:

[0008] Silicon-based anodes undergo volume expansion during lithium intercalation. If the electrode layer is too thick, the accumulated volume deformation can cause internal stress to exceed the material's yield strength, leading to particle pulverization and conductive network breakage. If the electrode layer is too thin, it is difficult to ensure coating uniformity, easily forming pinholes that can cause localized short circuits. This invention limits the thickness to the micrometer range, shortening the solid-phase diffusion path of lithium ions within and between silicon particles, thus reducing concentration polarization. More importantly, by using a hot-pressing pressure of 500MPa-650MPa and leveraging the lower Young's modulus of the sulfide electrolyte, the electrolyte particles undergo plastic deformation. The plastically flowing electrolyte fills the pores left by the expansion or contraction of the silicon particles and the gaps between particles, forming a tight physical contact structure inside the electrode. This highly dense structure can offset volume changes during subsequent cycling, maintaining the integrity of the interfacial contact.

[0009] The weight ratio is optimized based on the percolation threshold of the mixed ion-electron conductive network in the solid-state system. In the solid-state electrode, the active material particles must maintain effective contact with both the electronic and ion-conducting channels. The 30% and 25% electrolyte content in this invention ensures the continuity of the lithium-ion transport channels even with extremely low electrode porosity, preventing the active material from becoming an electrochemically inactive region due to ion isolation. Simultaneously, the 5% conductive agent and the proportion of the active material balance the relationship between energy density and power density, ensuring the reaction flux at the electrochemical reaction interface under high-rate charge-discharge conditions.

[0010] Preferably, the negative electrode active material layer is made of the following components in parts by weight: 60-70 parts of the negative electrode active material; 25-35 parts of the sulfide solid electrolyte; and 2-8 parts of the conductive agent. The positive electrode active material layer is made of the following components in parts by weight: 65-75 parts of the positive electrode active material; 20-30 parts of the sulfide solid electrolyte; and 2-8 parts of the conductive agent.

[0011] By adopting the above technical solution, a process window that adapts to fluctuations in the physical parameters of different batches of raw materials is provided while ensuring the core formulation ratio. Within the above component range, the electrode slurry has suitable rheological properties, which is conducive to achieving uniform coating of 4.0μm-6.0μm and preventing electrochemical performance inhomogeneity caused by component segregation.

[0012] Preferably, the sulfide solid electrolyte is The sulfide solid electrolyte powder is prepared by the following method: lithium sulfide, phosphorus pentasulfide and lithium chloride are mixed in a molar ratio of 5:1:2; the mixed raw materials are subjected to high-energy mechanical ball milling to obtain amorphous precursor powder; the amorphous precursor powder is heat-treated at 450℃-550℃ in an inert atmosphere, cooled and then pulverized.

[0013] By employing the above technical solution, a sulforaphane-germanium ore-type electrolyte with high ionic conductivity was prepared. Its reaction and phase transition mechanism are as follows:

[0014] Under the action of high-energy ball milling, the raw materials undergo a solid-phase reaction. The LiCl crystal structure is disrupted, and chemical bonds are broken and rearranged through mechanical force to form a crystal containing... Glassy intermediates of tetrahedral structural units enable atomic-scale mixing.

[0015] During the heat treatment process at 450℃-550℃, the glassy precursor undergoes structural rearrangement to achieve order, chloride ions enter the crystal lattice and occupy lattice sites, inducing the formation of a highly symmetric cubic crystal system. Crystal structure.

[0016] The electrolyte prepared by this method has high room temperature ionic conductivity and exhibits suitable deformation ability during subsequent hot pressing, which is beneficial for reducing grain boundary resistance.

[0017] Preferably, the bipolar all-solid-state battery further includes a common current collector with an interface resistance reduction layer, and the positive electrode active material layer is disposed on the side of the common current collector without the interface resistance reduction layer; the common current collector includes a metal foil substrate and an interface resistance reduction layer deposited on one surface of the metal foil substrate; the interface resistance reduction layer is a Li-PSO-based amorphous sulfide film. The metal foil substrate is a low-nickel alloy foil with a thickness of 8-12 μm; the interface resistance reduction layer has a thickness of 15-25 nm; the interface resistance reduction layer is formed by physical vapor deposition using a Li-PSO-based composite target.

[0018] By employing the above technical solution, the chemical incompatibility problem when sulfide electrolytes and metal current collectors are in direct contact is solved. Sulfur in sulfide electrolytes readily undergoes side reactions with metal current collectors, forming a high-resistance metal sulfide layer. A Li-PSO amorphous thin film serves as a buffer layer; the introduction of oxygen enhances the stability of chemical bonds, blocks sulfur diffusion, and prevents corrosion of the current collector. Simultaneously, the amorphous structure and nanoscale thickness ensure that lithium ions can penetrate this layer to reach the active material, achieving both electronic conduction and reducing interfacial contact resistance. Physical vapor deposition ensures the density and thickness uniformity of the film, avoiding pinhole defects.

[0019] Preferably, the solid electrolyte layer located between the positive electrode active material layer and the negative electrode active material layer is a dense film layer deposited by radio frequency magnetron sputtering; the average thickness of the solid electrolyte layer is 1.5 μm-2.5 μm.

[0020] By adopting the above technical solution, a solid electrolyte layer is directly grown on the electrode surface using vapor deposition technology, achieving two effects compared to coating or cold pressing processes:

[0021] Reducing the electrolyte layer thickness to 1.5μm-2.5μm decreases the volume and mass of inactive components, improves the volumetric energy density of the battery, and reduces ohmic impedance.

[0022] During magnetron sputtering, high-energy particles collide with the substrate to deposit, resulting in fewer grain boundary voids in the film layer. This eliminates the physical space for lithium dendrite growth, effectively preventing micro-short circuits between the positive and negative electrodes and ensuring insulation reliability even with thin film thickness.

[0023] Preferably, the temperature of the hot pressing treatment is 170℃-190℃, and the holding time is 20-40 minutes.

[0024] By adopting the above technical solution, long-term pressure holding is carried out in a range slightly lower than the glass transition temperature or crystallization temperature of sulfide electrolytes. On the one hand, this promotes the fusion between electrolyte particles and eliminates grain boundaries; on the other hand, this temperature range avoids high-temperature decomposition of the electrolyte or violent thermochemical reactions with active materials, thus ensuring the chemical stability of the battery materials.

[0025] Preferably, the The average particle size of the sulfide solid electrolyte powder is controlled to be below 0.5 μm.

[0026] By adopting the above technical solution, submicron-sized electrolyte particles have a higher specific surface area. When mixed with micron-sized active material particles, they increase the adhesion coverage on the surface of the active material, thereby constructing a more continuous and efficient ion transport network at a lower electrolyte volume fraction and reducing the generation of electrochemically inactive regions.

[0027] This invention provides a long-life, high-output-power bipolar all-solid-state battery. It has the following beneficial effects:

[0028] 1. This invention solves the problems of volume expansion and interface contact of silicon-based anodes in all-solid-state systems by strictly controlling the thickness of the negative electrode active material layer to 4.0μm to 6.0μm and using a high-pressure hot-pressing process of 500MPa to 650MPa. This thickness range balances the transport path length of lithium ions in the solid phase with the mechanical stability of the electrode structure, avoiding the decrease in kinetic performance caused by thick electrodes and the fragility of the conductive network of thin electrodes. The high-pressure process causes the sulfide electrolyte to undergo plastic deformation, fully filling the interparticle gaps and suppressing stress accumulation and interface peeling during cycling, thereby ensuring the battery's excellent cycle life and low internal resistance growth rate.

[0029] 2. This invention introduces a Li-PSO-based amorphous sulfide film as an interface resistance reduction layer on the surface of the common current collector, which improves the chemical compatibility between the sulfide solid electrolyte and the metal current collector. This modified layer physically blocks the direct contact between the active material and the current collector, preventing the formation of a high-resistance layer due to interfacial side reactions and reducing the interfacial contact resistance. This not only improves the charging and discharging efficiency of the battery, but also improves the power output characteristics of the battery under low temperature and high rate conditions.

[0030] 3. This invention utilizes radio frequency magnetron sputtering technology to construct a micron-scale dense solid electrolyte layer, which significantly shortens the lithium-ion transmission distance and reduces the ohmic impedance of the battery while ensuring reliable electronic insulation. Combined with a bipolar stacked structure design, the ultra-thin electrolyte layer reduces the volume ratio of inactive components, improves the volumetric energy density and mass power density of the all-solid-state battery, and meets the dual requirements of high energy density and high power output. Detailed Implementation

[0031] Preparation Examples 1-4:

[0032] Preparation Example 1:

[0033] This preparation example provides a method A method for preparing sulfide solid electrolyte powder includes the following steps:

[0034] In a high-purity argon atmosphere glove box with a dew point below -60°C, lithium sulfide, phosphorus pentasulfide, and lithium chloride were weighed and mixed in a molar ratio of 5:1:2.

[0035] The mixed powder was loaded into a zirconia ball mill jar and subjected to high-energy mechanical ball milling using a planetary ball mill. The rotation speed was set to 500 rpm and the ball milling time was 20 hours to obtain amorphous precursor powder.

[0036] The obtained precursor powder was placed in a heating furnace and heat-treated at 500°C for 2 hours under an argon atmosphere to promote crystallization.

[0037] After heat treatment, the product was cooled to room temperature in the furnace, and then pulverized and graded to obtain particles with an average particle size controlled below 0.5 μm. It is a sulfide solid electrolyte powder.

[0038] Preparation Example 2:

[0039] This preparation example provides a method for preparing a positive electrode composite material slurry, including the following steps:

[0040] In a high-purity argon atmosphere with a dew point below -60°C, the positive electrode active material lithium nickel cobalt manganese oxide was weighed and prepared as described in Example 1. The mixture consists of sulfide solid electrolyte powder and conductive agent acetylene black, with a weight ratio of 70:25:5.

[0041] The above solid components were added to an appropriate amount of anhydrous heptane solvent and mixed and dispersed using a high-speed disperser until a uniformly dispersed positive electrode composite slurry without obvious agglomeration was obtained.

[0042] Preparation Example 3:

[0043] This preparation example provides a method for preparing a negative electrode composite material slurry, including the following steps:

[0044] In a high-purity argon atmosphere with a dew point below -60°C, the negative electrode active material silicon powder was weighed and the product obtained in Example 1 was prepared. The mixture consists of sulfide solid electrolyte powder and conductive agent acetylene black, with a weight ratio of 65:30:5.

[0045] The above solid components were added to an appropriate amount of anhydrous heptane solvent and mixed using a combination of ultrasonic dispersion and mechanical stirring to prepare a uniformly dispersed negative electrode composite slurry.

[0046] Preparation Example 4:

[0047] This preparation example provides a method for preparing a common current collector with an interface resistance reduction layer, including the following steps:

[0048] A 10μm thick low-nickel alloy foil was selected as the current collector substrate, and the surface was cleaned with anhydrous ethanol and dried.

[0049] The cleaned substrate is placed in the vacuum chamber of a physical vapor deposition (PVD) device;

[0050] Using a Li-PSO composite target, a Li-PSO amorphous sulfide film is deposited on one surface of a substrate as an interfacial resistance reduction layer. The thickness of the film is precisely controlled to 20 nm by controlling the deposition time.

[0051] After preparation, the sample was removed under an inert atmosphere to obtain a common current collector with an interfacial resistance reduction layer.

[0052] Examples 1-7:

[0053] Example 1:

[0054] This embodiment provides a long-life, high-output-power bipolar all-solid-state battery, including the following steps:

[0055] Take the common current collector with the interfacial resistance reduction layer obtained in Preparation Example 4, and uniformly coat the positive electrode composite material slurry obtained in Preparation Example 2 on the side without the interfacial resistance reduction layer using a doctor blade coating method; after coating, dry it in a drying room to form a positive electrode active material layer with a thickness of 5 μm.

[0056] The cathode active material layer described above was prepared by radio frequency magnetron sputtering to obtain the material obtained in Example 1. Using a target material made of sulfide solid electrolyte powder as the source, a dense solid electrolyte layer is deposited, with the average thickness of the layer controlled to be 2.0 μm.

[0057] On the surface of the solid electrolyte layer, the negative electrode composite material slurry obtained in Example 3 was uniformly coated using a doctor blade coating method; the coating amount and doctor blade gap were controlled, and after drying, a negative electrode active material layer with an average layer thickness of 5.0 μm was formed; then an external current collector was stacked on the surface of the negative electrode active material layer to form a single cell stacked structure.

[0058] The above-mentioned stacked structure was placed in a hot press and subjected to constant temperature and pressure hot pressing at 180°C and 550MPa for 30 minutes. After natural cooling, a bipolar all-solid-state battery was obtained.

[0059] Example 2:

[0060] This embodiment provides a long-life, high-output-power bipolar all-solid-state battery, including the following steps:

[0061] Take the common current collector with the interfacial resistance reduction layer obtained in Preparation Example 4, and uniformly coat the positive electrode composite material slurry obtained in Preparation Example 2 on the side without the interfacial resistance reduction layer using a doctor blade coating method; after coating, dry it in a drying room to form a positive electrode active material layer with a thickness of 5 μm.

[0062] A dense solid electrolyte layer is deposited on the surface of the above-mentioned positive electrode active material layer using radio frequency magnetron sputtering, and the average thickness of the layer is controlled to be 2.0 μm.

[0063] On the surface of the solid electrolyte layer, the negative electrode composite material slurry obtained in Example 3 was uniformly coated using a doctor blade coating method; by adjusting the coating process parameters, the average thickness of the negative electrode active material layer formed after drying was controlled to be 4.0 μm; then an external current collector was stacked to form a laminated structure.

[0064] The above-mentioned stacked structure was placed in a hot press and subjected to constant temperature and pressure hot pressing at 180°C and 550MPa for 30 minutes. After cooling, a bipolar all-solid-state battery was obtained.

[0065] Example 3:

[0066] This embodiment provides a long-life, high-output-power bipolar all-solid-state battery, including the following steps:

[0067] Take the common current collector with the interface resistance reduction layer obtained in Preparation Example 4, coat the positive electrode composite material slurry obtained in Preparation Example 2 on the side without the interface resistance reduction layer, and dry it to form a positive electrode active material layer with a thickness of 5 μm.

[0068] A dense solid electrolyte layer with an average thickness of 2.0 μm is deposited on the surface of the positive electrode active material layer.

[0069] The negative electrode composite material slurry obtained in Example 3 was coated on the surface of the solid electrolyte layer; by adjusting the coating process parameters, the average thickness of the negative electrode active material layer formed after drying was controlled to be 6.0 μm; then an external current collector was stacked to form a laminated structure.

[0070] The above-mentioned stacked structure was placed in a hot press and subjected to constant temperature and pressure hot pressing at 180°C and 550MPa for 30 minutes. After cooling, a bipolar all-solid-state battery was obtained.

[0071] Example 4:

[0072] This embodiment provides a long-life, high-output-power bipolar all-solid-state battery, including the following steps:

[0073] Take the common current collector with the interface resistance reduction layer obtained in Preparation Example 4, coat the positive electrode composite material slurry obtained in Preparation Example 2 on the side without the interface resistance reduction layer, and dry it to form a positive electrode active material layer with a thickness of 5 μm.

[0074] A dense solid electrolyte layer with an average thickness of 2.0 μm is deposited on the surface of the positive electrode active material layer.

[0075] The negative electrode composite material slurry obtained in Example 3 was coated on the surface of the solid electrolyte layer; the average thickness of the negative electrode active material layer formed after drying was controlled to be 5.0 μm; then an external current collector was stacked to form a laminated structure.

[0076] The above-mentioned stacked structure was placed in a hot press and subjected to constant temperature and pressure hot pressing at 180°C and 500MPa for 30 minutes. After cooling, a bipolar all-solid-state battery was obtained.

[0077] Example 5:

[0078] This embodiment provides a long-life, high-output-power bipolar all-solid-state battery, including the following steps:

[0079] Take the common current collector with the interface resistance reduction layer obtained in Preparation Example 4, coat the positive electrode composite material slurry obtained in Preparation Example 2 on the side without the interface resistance reduction layer, and dry it to form a positive electrode active material layer with a thickness of 5 μm.

[0080] A dense solid electrolyte layer with an average thickness of 2.0 μm is deposited on the surface of the positive electrode active material layer.

[0081] The negative electrode composite material slurry obtained in Example 3 was coated on the surface of the solid electrolyte layer; the average thickness of the negative electrode active material layer formed after drying was controlled to be 5.0 μm; then an external current collector was stacked to form a laminated structure.

[0082] The above-mentioned stacked structure was placed in a hot press and subjected to constant temperature and pressure hot pressing at 180°C and 650MPa for 30 minutes. After cooling, a bipolar all-solid-state battery was obtained.

[0083] Example 6:

[0084] This embodiment provides a long-life, high-output-power bipolar all-solid-state battery, including the following steps:

[0085] Take the common current collector with the interface resistance reduction layer obtained in Preparation Example 4, coat the positive electrode composite material slurry obtained in Preparation Example 2 on the side without the interface resistance reduction layer, and dry it to form a positive electrode active material layer with a thickness of 5 μm.

[0086] A dense solid electrolyte layer with an average thickness of 2.0 μm is deposited on the surface of the positive electrode active material layer.

[0087] The negative electrode composite material slurry obtained in Example 3 was coated onto the surface of the solid electrolyte layer; by adjusting the coating process parameters, the average thickness of the negative electrode active material layer formed after drying was controlled to be 4.0 μm; then an external current collector was stacked to form a laminated structure.

[0088] The above-mentioned stacked structure was placed in a hot press and subjected to constant temperature and pressure hot pressing at 180°C and 650MPa for 30 minutes. After cooling, a bipolar all-solid-state battery was obtained.

[0089] Example 7:

[0090] This embodiment provides a long-life, high-output-power bipolar all-solid-state battery, including the following steps:

[0091] Take the common current collector with the interface resistance reduction layer obtained in Preparation Example 4, coat the positive electrode composite material slurry obtained in Preparation Example 2 on the side without the interface resistance reduction layer, and dry it to form a positive electrode active material layer with a thickness of 5 μm.

[0092] A dense solid electrolyte layer with an average thickness of 2.0 μm is deposited on the surface of the positive electrode active material layer.

[0093] The negative electrode composite material slurry obtained in Example 3 was coated on the surface of the solid electrolyte layer; by adjusting the coating process parameters, the average thickness of the negative electrode active material layer formed after drying was controlled to be 6.0 μm; then an external current collector was stacked to form a laminated structure.

[0094] The above-mentioned stacked structure was placed in a hot press and subjected to constant temperature and pressure hot pressing at 180°C and 500MPa for 30 minutes. After cooling, a bipolar all-solid-state battery was obtained.

[0095] Comparative Examples 1-3:

[0096] Comparative Example 1:

[0097] Compared with Example 1, the difference is that the average thickness of the negative electrode active material layer formed after drying is controlled to be 10.0 μm, while the rest are the same.

[0098] Comparative Example 2:

[0099] Compared with Example 1, the difference is that the applied hot-pressing pressure is 300 MPa, and all other aspects are the same.

[0100] Comparative Example 3:

[0101] Compared with Example 1, the difference is that the average thickness of the negative electrode active material layer formed after drying is controlled to be 2.0 μm, while the rest are the same.

[0102] Test Examples 1-4:

[0103] Test Example 1: Electrochemical Impedance Spectroscopy (EIS) Test

[0104] Experimental description:

[0105] The test batteries prepared in the examples and comparative examples were placed in a constant temperature chamber at 25°C and left to stand for 2 hours to allow their internal temperature to reach equilibrium.

[0106] The batteries were pre-cycle activated using a charge-discharge tester, and then the state of charge (SOC) of all batteries was uniformly adjusted to 50%.

[0107] Connect the adjusted battery to the electrochemical workstation using a standard four-wire connection to eliminate the influence of clamp and wire resistance.

[0108] Set the AC impedance test parameters: frequency scan range of 1MHz to 10mHz, AC voltage disturbance amplitude of 10mV, and data acquisition under open circuit voltage conditions.

[0109] The acquired Nyquist plots were fitted and analyzed using ZView software based on the equivalent circuit model. The Ohmic impedance, representing the bulk impedance and contact impedance, and the charge transfer impedance, representing the electrode / electrolyte interface reaction process, were separated and the sum of the two was recorded as the total interface impedance of the battery.

[0110] Experimental data:

[0111] Table 1. Summary of Electrochemical Impedance Test Data for Examples and Comparative Examples

[0112]

[0113] Results analysis:

[0114] According to the data in Table 1, the total interfacial impedance of Examples 1 to 7 is all distributed between 13.5 and... The impedance values ​​are in the lower range, while the impedance values ​​of comparative examples 1 to 3 show varying degrees of increase.

[0115] Analysis of the effect of hot-pressing pressure on impedance, comparing Examples 1 and 5 (≥550MPa) with Comparative Example 2 (300MPa), shows that when the hot-pressing pressure is insufficient, the charge transfer impedance value surges dramatically. Sulfide solid electrolytes are inorganic ceramic materials. Although they possess a certain degree of room temperature ductility, the electrolyte particles only undergo sufficient plastic deformation under pressures exceeding the critical pressure (500 MPa). In the example, high-pressure treatment forces the electrolyte particles to fill the microscopic voids between the negative electrode active material particles, establishing a dense interfacial contact and reducing the interfacial contact barrier. In Comparative Example 2, due to a pressure of only 300 MPa, a large number of physical voids exist between the active material and the electrolyte, resulting in hindered lithium-ion cross-interface transport, manifested as extremely high charge transfer impedance.

[0116] Analyzing the effect of negative electrode layer thickness on impedance, comparing Examples 1, 2, and 3 with Comparative Examples 1 and 3 reveals that the size effect of negative electrode layer thickness exhibits nonlinear characteristics. In Comparative Example 1, the 10.0 μm thick electrode causes the charge transfer impedance to increase to [missing value]. This is because the tortuosity of the ion conduction path in a solid system increases exponentially with thickness, making it difficult for deep-layer active materials to participate in the reaction, resulting in a decrease in the effective reaction area and an increase in apparent impedance. Conversely, the 2.0 μm ultrathin electrode in Comparative Example 3 did not reduce impedance as expected; instead, its ohmic impedance and charge transfer impedance increased abnormally (ohmic impedance reached...). This is because it is difficult to construct a continuous and stable three-dimensional electronic conductive network in an excessively thin electrode coating. The discretization of the distribution of active material particles leads to some areas being in an electronic island state, which destroys the overall conductive integrity of the electrode.

[0117] In summary, the data from Examples 1 to 7 demonstrate that only by controlling the thickness of the negative electrode layer within the range of 4.0-6.0 μm and employing a high-pressure hot-pressing process of 500-650 MPa can the atomic-level close contact between the electrolyte and the active material be achieved while ensuring the connectivity of the electronic network, thereby minimizing the total interfacial impedance within the battery.

[0118] Test Example 2: Low Temperature High Rate Discharge Performance Test

[0119] Experimental description:

[0120] The battery under test was placed in an ambient temperature of 25°C and charged at a constant current rate of 0.1C to the cutoff voltage of 4.2V. Then it was charged at a constant voltage until the current dropped to 0.01C to ensure that the battery was fully charged.

[0121] Transfer the fully charged battery to a temperature-controlled chamber, set the chamber temperature to -20℃, and leave it to stand for 4 hours to allow the temperature of the internal components of the battery to reach complete thermal equilibrium with the ambient temperature.

[0122] At -20℃, the discharge current density is set to... (Approximately corresponding to a 5C rate) Perform constant current discharge on the battery until the voltage drops to 2.0V and is then cut off.

[0123] Collect capacity data and median discharge voltage during the discharge process, and calculate the mass power density (W / kg) and low-temperature capacity retention rate (relative to 25℃ 0.1C discharge capacity) of each battery group by combining the mass of the individual battery cells (excluding the casing).

[0124] Experimental data:

[0125] Table 2. Summary of Low-Temperature High-Rate Discharge Performance Data of Batteries in Examples and Comparative Examples

[0126]

[0127] Results analysis:

[0128] According to the data in Table 2, under the conditions of -20℃ low temperature and high current density, the initial output power density of Examples 1 to 7 remained above 730W / kg, with the highest reaching 761.2W / kg (Example 6), while the performance indicators of the comparative examples all showed a decrease.

[0129] An analysis of the impact of negative electrode layer thickness revealed that Comparative Example 1 (10.0 μm) exhibited a power density of only 603.8 W / kg, with a median discharge voltage dropping to 3.25 V. This is because, at low temperatures, the lithium-ion diffusion coefficient within the sulfide solid electrolyte and active material decreases. When the electrode layer thickness exceeds 6.0 μm, the ion transport path within the solid phase lengthens, concentration polarization increases significantly, leading to an premature drop in the discharge plateau voltage and limited effective energy output. Conversely, Comparative Example 3 (2.0 μm) showed the lowest power density at only 452.1 W / kg, with extremely low capacity utilization. This is because an extremely thin electrode layer makes it difficult to form a uniform and continuous conductive network during coating, resulting in excessive local internal resistance and a severe ohmic voltage drop during high-rate discharge, causing the battery to rapidly reach the cutoff voltage. Examples 1 to 7 controlled the negative electrode layer thickness within the range of 4.0-6.0 μm, balancing the ion transport distance with the stability of the electronic conductive network, ensuring high-performance output at low temperatures and high rates.

[0130] An analysis of the effect of hot-pressing pressure was conducted, comparing Example 1 (550 MPa, 752.1 W / kg) with Comparative Example 2 (300 MPa, 678.5 W / kg). The battery prepared under low pressure exhibited poor voltage retention under low-temperature, high-load conditions. This is because low temperatures exacerbate material shrinkage. If the initial mechanical interlocking force at the interface is insufficient (i.e., low hot-pressing pressure), the interface contact area further decreases under the dual stress of low temperature and high outflow, leading to increased interface impedance and thus reduced output power. The examples employed high-pressure hot-pressing above 500 MPa, constructing a dense interface sufficient to withstand low-temperature shrinkage stress, thus ensuring excellent power characteristics.

[0131] Test Example 3: Long Cycle Life Performance Test

[0132] Experimental description:

[0133] The battery under test was fixed in a stainless steel fixture, and a constant restraint pressure (10 MPa) was applied to simulate the assembly environment inside the battery pack. Then it was placed in a constant temperature test cabinet at 25°C and left to stand for 3 hours.

[0134] The charge / discharge voltage range is set to 2.5V to 4.2V. Three charge / discharge cycles are performed at a low rate of 0.1C. The discharge capacity of the third cycle is taken as the initial discharge capacity of the battery.

[0135] Adjust the charge / discharge rate to 0.5C, perform constant current charging to 4.2V, let it stand for 10 minutes, then perform constant current discharging to 2.5V, and let it stand for 10 minutes. This process is defined as a complete cycle.

[0136] Perform 500 charge-discharge cycles as described above, record the discharge capacity of each cycle in real time, and calculate the ratio of the discharge capacity of the 500th cycle to the initial discharge capacity after the test to obtain the capacity retention rate.

[0137] Experimental data:

[0138] Table 3. Summary of 500-cycle life test data for the batteries in the examples and comparative examples

[0139]

[0140] Results analysis:

[0141] According to the data in Table 3, after 500 charge-discharge cycles, the capacity retention rate of Examples 1 to 7 remained at a high level of 84.6% to 92.1%, while the capacity decay of Comparative Example 2 was the most severe, with only 65.2% remaining.

[0142] The effect of hot-compression pressure on cycling stability was analyzed, comparing the data differences between Examples 1 and 5 (≥550 MPa) and Comparative Example 2 (300 MPa). Silicon-based anode materials undergo approximately 300% volume change during lithium insertion / extraction. This repeated volume breathing effect easily generates shear stress at the interface between the active material and the solid electrolyte. In Comparative Example 2, due to insufficient initial hot-compression pressure, only limited point contact was formed between the electrolyte and active material particles, resulting in weak mechanical interlocking. During long-term cycling, the stress accumulation caused by volume expansion exceeded the interfacial bonding force, triggering physiological delamination, leading to a significant loss of electrochemical activity in the active material and a rapid capacity drop. Examples 1 and 5, through high-pressure treatment above 550 MPa, promoted sufficient plastic flow of the sulfide electrolyte, filling the micropores between particles and forming a dense interface with high mechanical strength. This effectively suppressed interlayer separation caused by volume effects, thereby achieving an excellent capacity retention rate of over 91%.

[0143] The impact of negative electrode layer thickness on cycle stability was analyzed, comparing Example 1 and Comparative Example 1 (10.0 μm). With increasing electrode thickness, the volume change gradient of the electrode layer along the thickness direction increases during charge and discharge, exacerbating the stress mismatch between deep and surface particles. This makes it easier for microcracks to form inside the thicker electrode, cutting off electron transport paths and causing the capacity retention rate of Comparative Example 1 to decrease to 78.4%. Furthermore, although Comparative Example 3 (2.0 μm) had a relatively good capacity retention rate (88.5%), its initial capacity (92.1 mAh / g) was far lower than that of the Example 1. This is because the excessively thin coating resulted in insufficient total active material loading and uneven distribution, leading to a loss of practical value for the overall battery energy density. The Example 1, by optimizing the thickness to 4.0-6.0 μm, effectively mitigated the structural stress concentration problem caused by volume changes while ensuring high energy density.

[0144] Test Example 4: DC Internal Resistance (DCIR) Growth Rate Test During Cyclic Process

[0145] Experimental description:

[0146] Select fresh, uncycled batteries from each group and place them in a constant temperature environment of 25°C for 2 hours to adjust the state of charge (SOC) to 50%.

[0147] A discharge pulse lasting 10 seconds is applied to the battery, with the discharge current set to 1C. The voltage drop at the moment of the pulse is recorded using a high-precision voltage acquisition system, and the initial DC internal resistance before cycling is calculated based on Ohm's law.

[0148] The battery was subjected to 500 charge-discharge cycles under the cycling conditions described in Test Example 3.

[0149] After the cycle is completed, the battery is allowed to rest and its state of charge is readjusted to 50%. The same discharge pulse is applied again, and the DC internal resistance after the cycle is measured.

[0150] Based on the formula: Internal resistance growth rate (%) = ((Cyclic DC internal resistance - Initial DC internal resistance) / Initial DC internal resistance) × 100%, calculate the degree of internal resistance degradation of each group of batteries during long-term cycling.

[0151] Experimental data:

[0152] Table 4. Summary of DC internal resistance changes before and after battery cycling in the examples and comparative examples

[0153]

[0154] Results analysis:

[0155] According to the data in Table 4, the internal resistance growth rate of Examples 1 to 7 was controlled between 17.2% and 34.2%, showing good interface stability; while the internal resistance growth rates of Comparative Examples 2 and 3 were as high as 183.1% and 81.0%, respectively, showing serious deterioration of the internal structure.

[0156] Analysis of the impact of hot-pressing pressure revealed that Comparative Example 2 (300 MPa) had an initial internal resistance as high as 52.6 Ω, which surged to 148.9 Ω after cycling, nearly doubling in rate. This directly verifies that low-pressure hot-pressing cannot establish a strong physical bond between the sulfide electrolyte and the active material. During cycling, the repeated volume expansion and contraction of the negative electrode active material generates enormous mechanical stress. Due to the lack of tight mechanical interlocking, the active material particles gradually detach from the electrolyte interface, resulting in a sharp decrease in contact area and an exponential increase in contact resistance. In contrast, Example 5 (650 MPa) achieved a dense bond between materials through an ultra-high pressure process, effectively resisting interfacial peeling caused by volume changes and controlling the internal resistance growth rate to an extremely low level of 17.9%.

[0157] Analysis of the impact of negative electrode layer thickness revealed the structural fragility of ultrathin electrodes through the high internal resistance growth rate (81.0%) of Comparative Example 3 (2.0 μm). In excessively thin coatings, the conductive agent (acetylene black) struggles to construct a sufficiently redundant three-dimensional conductive network. As cycling progresses, some conductive nodes break due to microscopic displacement, causing active material particles to become dead zones due to the loss of electron pathways, leading to an increase in macroscopic resistance. Examples 1 to 7 optimized the thickness to 4.0-6.0 μm, ensuring the connectivity and robustness of the conductive network, thus maintaining a lower internal resistance growth rate during long-term cycling. While Comparative Example 1 (10.0 μm) exhibited better initial conductivity than Comparative Example 3, the increased thickness led to stress accumulation, making the layer more prone to crack formation, resulting in a higher internal resistance growth rate (58.9%) compared to the examples.

Claims

1. A long-life, high-output-power bipolar all-solid-state battery, characterized in that, It includes at least one single-cell stacked structure, wherein the single-cell stacked structure comprises, in spatial order, a positive electrode active material layer, a solid electrolyte layer and a negative electrode active material layer; The average thickness of the negative electrode active material layer is 4.0 μm-6.0 μm; The bipolar all-solid-state battery is a dense structure formed by hot-pressing the single-cell stacked structure under a pressure of 500MPa-650MPa. The weight ratio of negative electrode active material, sulfide solid electrolyte and conductive agent in the negative electrode active material layer is 65:30:

5. The weight ratio of the active material, the sulfide solid electrolyte, and the conductive agent in the positive electrode active material layer is 70:25:

5.

2. The long-life high-power all-solid-state bipolar battery according to claim 1, characterized by, The negative electrode active material layer is made of components comprising the following parts by weight: The negative electrode active material is 60-70 parts; 25-35 parts of the sulfide solid electrolyte; And 2-8 parts of the conductive agent.

3. The long-life high-power all-solid-state bipolar battery according to claim 2, characterized by The positive electrode active material layer is made of components comprising the following parts by weight: The positive electrode active material is 65-75 parts; 20-30 parts of the sulfide solid electrolyte; And 2-8 parts of the conductive agent.

4. The long-life, high-output-power bipolar all-solid-state battery according to claim 3, characterized in that, The sulfide solid electrolyte is A sulfide solid electrolyte powder is prepared by the following preparation method: Lithium sulfide, phosphorus pentasulfide and lithium chloride are mixed in a molar ratio of 5:1:

2. The mixed raw materials were subjected to high-energy mechanical ball milling to obtain amorphous precursor powder; The amorphous precursor powder was heat-treated at 450℃-550℃ in an inert atmosphere, cooled, and then pulverized.

5. The long-life high-power all-solid-state bipolar battery according to claim 1, wherein The bipolar all-solid-state battery also includes a common current collector with an interface resistance reduction layer, and the positive electrode active material layer is disposed on the side of the common current collector without the interface resistance reduction layer. The common current collector includes a metal foil substrate and an interface resistance reduction layer deposited on one side surface of the metal foil substrate; The interface resistance reduction layer is a Li-PSO-based amorphous sulfide film.

6. A long-life, high-output-power bipolar all-solid-state battery according to claim 5, characterized in that, The metal foil substrate is a low-nickel alloy foil with a thickness of 8-12 μm; The thickness of the interface resistance reduction layer is 15-25 nm; The interface resistance reduction layer is formed by physical vapor deposition using a Li-PSO composite target.

7. A long-life, high-output-power bipolar all-solid-state battery according to claim 1, characterized in that, The solid electrolyte layer located between the positive electrode active material layer and the negative electrode active material layer is a dense film layer deposited using radio frequency magnetron sputtering. The average thickness of the solid electrolyte layer is 1.5 μm-2.5 μm.

8. A long-life, high-output-power bipolar all-solid-state battery according to claim 1, characterized in that, The hot pressing process is carried out at a temperature of 170℃-190℃ and a holding time of 20-40 minutes.

9. A long-life, high-output-power bipolar all-solid-state battery according to claim 3, characterized in that, The negative electrode active material is silicon powder, the positive electrode active material is lithium nickel cobalt manganese oxide, and the conductive agent is acetylene black.

10. A long-life, high-output-power bipolar all-solid-state battery according to claim 4, characterized in that, The The average particle size of the sulfide solid electrolyte powder is controlled to be below 0.5 μm.

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