Solid-state battery and formation method

Abstract

The application provides a solid-state battery and a formation method, which comprises the following steps: applying a pressure P1 to the surface of the battery, charging at a C1 rate constant current to a Q1 state of charge, and resting for a t1 time; reducing the pressure to P2, resting for a t2 time; charging at a C2 rate constant current under the condition of P2 to a Q2 state of charge, resting for a t3 time, and C2 is greater than C1; reducing the pressure to P3, resting for a t4 time; increasing the pressure to P4, resting for a t5 time, and P4 is greater than P2; discharging at a C3 rate constant current under the condition of P4 to a Q3 state of charge, resting for a t6 time, and completing a charge-discharge cycle of formation. In the formation process, the external pressure is dynamically adjusted according to the battery SOC, the initial contact energy barrier of the solid-solid interface is overcome, the volume change of the electrode material in the charge-discharge process is adapted, the material structure damage or ion migration obstruction caused by excessive compression is avoided, and the cycle performance of the battery is improved.

Description

Technical Field

[0001] This application relates to the field of solid-state batteries, and more particularly to a solid-state battery and its formation method. Background Technology

[0002] The formation process of solid-state batteries (i.e. the initial charge-discharge activation process) directly affects their interface contact quality, ionic conductivity, and cycle performance.

[0003] In some formation processes, a fixed pressure is used to form solid-state lithium-ion batteries. However, the expansion of electrode materials during the charging process of solid-state batteries will increase their thickness and internal stress, which may cause structural damage to the materials and hinder ion migration, resulting in the battery performance after formation failing to meet theoretical expectations.

[0004] Therefore, designing a formation process that conforms to the characteristics of solid-state battery materials is an urgent problem to be solved. Summary of the Invention

[0005] This application provides a solid-state battery and a formation method, which provides a formation process that conforms to the characteristics of solid-state battery materials.

[0006] In a first aspect, this application provides a method for forming a solid-state battery, comprising the following steps:

[0007] Apply pressure P1 to the surface of the battery, charge the battery at a constant current rate of C1 until it reaches the Q1 state of charge, and then leave it for a time t1.

[0008] Reduce the pressure to P2 and hold for time t2;

[0009] Under the P2 condition, the battery is charged at a constant current rate of C2 until it reaches a state of charge Q2, and then left to stand for a time t3, where C2 is greater than C1.

[0010] Reduce the pressure to P3 and hold for t4 time;

[0011] The pressure is increased to P4, and then held for t5, where P4 is greater than P2.

[0012] Under the P4 condition, the battery is discharged at a constant current rate of C3 until it reaches the Q3 state of charge, and then left to stand for t6 time to complete one charge-discharge cycle of formation.

[0013] Furthermore, P1 is 10-20 MPa, P2 is 8-15 MPa, P3 is 5-10 MPa, P4 is 10-20 MPa, and P1 > P2 > P3.

[0014] Furthermore, C1 is 0.05~0.1C, and C2 is 0.2~0.3C.

[0015] Furthermore, Q1 is 15~30% SOC, Q2 is 55~100% SOC, and Q3 is 0~10% SOC.

[0016] Furthermore, the temperature T1 of the formation process is 35~100℃.

[0017] Furthermore, T1 is 35~45℃.

[0018] Furthermore, t1 is 5~10 min, t2 is 1~2 h, t3 is 10~20 min, t4 is 1~2 h, t5 is 1~2 h, and t6 is 2~4 h.

[0019] Furthermore, the rate of pressure reduction to P2 is v1, which is 0.01~0.03 MPa / s; the rate of pressure reduction to P3 is v2, which is 0.05~0.07 MPa / s; and the rate of pressure increase to P4 is v3, which is 0.06~0.1 MPa / s.

[0020] Furthermore, a flexible buffer pad of 0.2~0.5mm is provided on the surface of the pressure clamp and the battery.

[0021] Secondly, this application provides a solid-state battery, which is prepared by the formation method described in any one of the first aspects.

[0022] This application provides a solid-state battery and a formation method. The method includes the following steps: applying pressure P1 to the battery surface; charging the battery at a constant current rate of C1 to a state of charge (Q1); and resting for time t1; reducing the pressure to P2 and resting for time t2; under the condition of P2, charging the battery at a constant current rate of C2 to a state of charge (Q2); and resting for time t3, where C2 is greater than C1; reducing the pressure to P3 and resting for time t4; increasing the pressure to P4 and resting for time t5, where P4 is greater than P2; and under the condition of P4, discharging the battery at a constant current rate of C3 to a state of charge (Q3); and resting for time t6, thus completing one charge-discharge cycle of the formation. Through this method, the external pressure is dynamically adjusted according to the battery's state of charge (SOC) during the formation process, overcoming the initial contact barrier at the solid-solid interface, while adapting to the volume changes of the electrode material during charge and discharge. This avoids excessive pressure that could damage the material structure or hinder ion migration, thereby improving the battery's cycle performance. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0024] Figure 1A schematic flowchart of a solid-state battery formation method provided in this application;

[0025] Figure 2 A schematic diagram of the battery provided in this application.

[0026] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0027] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as any other stated value or each smaller range between intermediate values ​​within a range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This application specification and embodiments are merely exemplary.

[0029] Currently, the formation process of all-solid-state lithium-ion batteries adopts the formation scheme of liquid batteries: it is usually carried out at a high temperature of 60-100℃, and the electrode materials are gradually activated and a stable solid electrolyte interphase (SEI) film is formed through static pressure and constant current (such as 0.05-0.1C) charge-discharge cycles. However, the solid-solid interface contact characteristics of all-solid-state batteries are very different from those of liquid batteries. The solid electrolyte needs to achieve electrode contact, ion conduction and electronic insulation functions simultaneously. The initial contact energy barrier of the interface is high, and the electrode materials will undergo volume expansion / contraction during charge and discharge, resulting in dynamic changes in interface stress. Using a single static pressure may lead to material structure damage or ion migration obstruction.

[0030] In view of this, this application achieves dynamic contact optimization of the solid-solid interface and adaptive matching of electrode expansion / contraction stress in all-solid-state lithium-ion batteries through a dynamic pressure-controlled formation method. Specifically, during the formation process, the external pressure is dynamically adjusted according to the battery's SOC to overcome the initial contact energy barrier at the solid-solid interface, while adapting to the volume changes of the electrode material during charging and discharging.

[0031] Figure 1 A schematic flowchart of a solid-state battery formation method provided in this application is shown below. Figure 1 As shown, it includes the following steps:

[0032] S1. Apply pressure P1 to the battery surface and charge the battery at a constant current rate of C1 until Q1 is reached, then let it rest for time t1.

[0033] S2. Reduce the pressure to P2 and hold for time t2.

[0034] S3. Under P2 conditions, the battery is charged at a constant current rate of C2 until Q2 is reached. After resting for t3, C2 is greater than C1.

[0035] S4. Reduce the pressure to P3 and hold for t4 hours.

[0036] S5. Increase the pressure to P4 and hold for t5 time. P4 is greater than P2.

[0037] S6. Under P4 conditions, the battery is discharged at a constant current rate of C3 until Q3 is reached. After a resting time of t6, one charge-discharge cycle of formation is completed.

[0038] In step S1, during the initial stage of formation (low SOC), a higher pressure (P1) is applied to overcome the initial contact energy barrier at the solid-solid interface, ensuring the establishment of ion transport channels.

[0039] In step 2, as the charging process progresses (SOC increases), the negative electrode expands, increasing internal stress. Excessive external pressure can lead to microcracks and fragmentation in either the negative or positive electrode materials, resulting in failure. Furthermore, it can cause excessive local material embedding and slippage, even triggering interface debonding or migration, leading to poor contact or increased impedance. This is especially true at high SOCs, where the significant volume expansion of the negative electrode exacerbates interfacial mechanical conflicts, inducing interface peeling or pulverization. Ion migration in solid electrolytes relies on migration channels within the crystal structure; high pressure can compress or collapse these channels, increasing the migration barrier and significantly reducing ion diffusion rate.

[0040] Therefore, in step S2, the externally applied pressure is reduced to avoid excessive pressure that could damage the material structure or hinder ion migration.

[0041] By allowing the lithium ions to rest under P2 pressure for t2 time, they can be further inserted into the negative electrode without being crushed, thus enhancing interface activation.

[0042] During the electrode expansion stage, if the external pressure is not reduced synchronously, it will compress the porosity inside the electrode, making it impossible for the active particles to smoothly accommodate the volume expansion, resulting in dense accumulation and blockage of the ion diffusion path.

[0043] In step S3, under pressure P2, the formation current is increased to C2, and the battery is charged to Q2 SOC%, which increases the formation speed, shortens the formation time, improves production efficiency, and reduces manufacturing costs. Because the interface contact has been optimized and preliminary activation has been performed in the preceding steps, it is safe to slightly increase the current (C2 > C1) at this stage. A slightly higher current density promotes a more uniform and faster film formation reaction on the electrode surface, reduces the diffusion of side reactions into the electrode depth, thereby forming a thinner, denser, and more conductive interface film, reducing interface impedance, facilitating lithium-ion migration, and improving battery performance.

[0044] In step S4, as charging proceeds, the volume of the negative electrode increases, and its internal stress increases. The pressure decreases to P3, giving the battery a chance to "relax" and avoid being "crushed," which could hinder the continued intercalation of lithium ions or cause particle breakage.

[0045] By allowing the electrode and solid electrolyte interface to rest for t4 under this P3 pressure, fine-tuning and the establishment of a new equilibrium are possible under low stress, ensuring that lithium ions can be more thoroughly intercalated and enhancing the interface activation effect.

[0046] In step S5, the pressure is increased to prepare for discharge. During discharge, lithium ions escape from the negative electrode and return to the positive electrode, causing the negative electrode material to shrink. If the pressure is still low at this time (P3), the interface contact will become loose, and even micro-gap will form, resulting in a sharp increase in interface impedance, making discharge difficult and potentially uneven. Therefore, the pressure is slowly increased from N3 back to the initial higher pressure P4. The purpose is to re-compact the electrode interface, which may have become loose due to discharge shrinkage, before the start of discharge, ensuring that the solid-solid contact remains in good condition throughout the discharge process.

[0047] The P4 pressure is held for t5 time to allow the battery system to adapt to the pressure, so that the interface contact reaches a stable and tight state, providing an ideal and stable mechanical environment for subsequent constant current discharge.

[0048] In step S6, discharging under the established good contact pressure (P4) ensures that the lithium-ion extraction process from the negative electrode is uniform and efficient, preventing excessive local current, lithium metal deposition, or interface damage caused by poor contact. The discharge process not only releases capacity but may also involve the further formation or stabilization of the positive electrode interface film (CEI). Performing this operation under P4 pressure helps to form a higher quality interface film.

[0049] Discharging to a specific Q3 SOC (typically a lower value such as 5% or 10%) completes the first full charge-discharge cycle, thus accurately calibrating the battery's actual capacity (initial coulombic efficiency). A rest period of t6 is used to allow voltage and interface states to reach equilibrium.

[0050] By employing a method that dynamically controls the formation pressure and SOC (State of Charge), the charging process involves reducing the pressure on the battery surface. This ensures that lithium ions can be more thoroughly intercalated during the negative electrode expansion, enhancing the interface activation effect and preventing "crushing" that could hinder further lithium ion intercalation or cause particle breakage. This method maximizes the activation of electrode material performance during battery formation, thereby improving charge / discharge efficiency and cycle performance.

[0051] It should be noted that the above process is only one charge-discharge cycle, and the entire formation process may include multiple charge-discharge cycles. Each charge-discharge cycle includes the aforementioned pressure reduction and then resting phase during the charging process.

[0052] In step S2, there are several ways to reduce the pressure to P2.

[0053] In one specific implementation, the pressure is reduced from P1 to P2 at a fixed rate.

[0054] In one specific implementation, the pressure reduction from P1 to P2 is divided into several decreasing plateaus, with each plateau paused for a period of time. For example, the pressure is slowly reduced from P1 to P10, paused for a period of time, then slowly reduced to P11, paused for a period of time, and then reduced to P2.

[0055] In some embodiments, P1 is 10-20 MPa, such as 10 MPa, 12 MPa, 14 MPa, 16 MPa, 18 MPa, 20 MPa, or any combination of the above.

[0056] In some embodiments, P2 is 8-15 MPa, such as 8 MPa, 9 MPa, 10 MPa, 11 MPa, 13 MPa, 15 MPa, or any combination thereof. P2 is less than P1.

[0057] In some embodiments, P3 is 5-10 MPa, such as 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, or any combination thereof. P3 is less than P2.

[0058] In some embodiments, P4 is 10-20 MPa. For example, 10 MPa, 12 MPa, 14 MPa, 16 MPa, 18 MPa, 20 MPa, or any combination of the above.

[0059] In some embodiments, P4 equals P1.

[0060] In some embodiments, C1 is 0.05~0.1C, such as 0.05C, 0.06C, 0.07C, 0.08C, 0.09C, 0.10C, or any combination thereof. C2 is 0.2~0.3C, such as 0.2C, 0.22C, 0.24C, 0.26C, 0.28C, 0.30C, or any combination thereof. A C2 greater than C1 promotes a more uniform and rapid film-forming reaction on the electrode surface, reduces the diffusion of side reactions into the electrode depth, and thus forms a thinner, denser, and more conductive interface film. It also reduces side reaction time, reduces irreversible capacity loss, thereby improving the initial coulombic efficiency and increasing the final usable capacity of the battery.

[0061] In some embodiments, Q1 is 15-30% SOC, such as 15% SOC, 18% SOC, 20% SOC, 24% SOC, 27% SOC, 30% SOC, or any combination thereof. The initial charging stage is a period of active interfacial reactions, which easily leads to the formation of unstable byproducts (such as Li2S, Li2O, etc.). Controlling the SOC at 15-30% limits the reaction depth, avoids violent side reactions, and is beneficial for building a dense and stable solid-solid interface. Initially, only a small portion of lithium is intercalated, which is conducive to the gradual establishment of ion channels and a good contact interface between the electrode and the solid electrolyte, reducing interfacial impedance.

[0062] In some embodiments, Q2 is 55-100% SOC, such as 55% SOC, 60% SOC, 70% SOC, 80% SOC, 90% SOC, 100% SOC, or any combination thereof. Continuing charging after pressure reduction to increase SOC allows the electrode structure to gradually adapt to its existing expansion, reducing the risk of interface peeling or debonding. Preferably, Q2 is 55-80% SOC to avoid interfacial side reactions or structural damage caused by high SOC.

[0063] In some embodiments, Q3 is 0 to 10% SOC, such as 0% SOC, 2.5% SOC, 5% SOC, 7.5% SOC, 10% SOC, or any combination of the above.

[0064] In some embodiments, T1 is 35~100°C, such as 35°C, 45°C, 60°C, 80°C, 100°C, or any combination of the above.

[0065] Preferably, T1 is 35~45℃. Dynamic pressure regulation optimizes interface contact and reduces interface impedance, thereby compensating for the decrease in ionic conductivity caused by temperature reduction. Formation can be completed at 35~45℃, which is beneficial to improving battery safety.

[0066] In some embodiments, t1 is 5 to 10 minutes, such as 5 minutes, 6 minutes, 7 minutes, 8 minutes, 10 minutes, or any combination of the above; t2 is 1 to 2 hours, such as 1 hour, 1.2 hours, 1.5 hours, 1.7 hours, 2 hours, or any combination of the above; t3 is 10 to 20 minutes, such as 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes, 20 minutes, or any combination of the above; t4 is 1 to 2 hours, such as 1 hour, 1.2 hours, 1.5 hours, 1.7 hours, 2 hours, or any combination of the above; t5 is 1 to 2 hours, such as 1 hour, 1.2 hours, 1.5 hours, 1.7 hours, 2 hours, or any combination of the above; t6 is 2 to 4 hours, such as 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, or any combination of the above.

[0067] In some embodiments, the rate of voltage reduction to P2, v1, is 0.01~0.03 MPa / s, for example, 0.01 MPa / s, 0.02 MPa / s, 0.03 MPa / s, or any combination thereof; the rate of voltage reduction to P3, v2, is 0.05~0.07 MPa / s, for example, 0.05 MPa / s, 0.06 MPa / s, 0.07 MPa / s, or any combination thereof; and the rate of voltage increase to P4, v3, is 0.06~0.1 MPa / s, for example, 0.06 MPa / s, 0.07 MPa / s, 0.08 MPa / s, 0.09 MPa / s, 0.10 MPa / s, or any combination thereof.

[0068] In some embodiments, the pressure clamp and the surface of the battery are provided with a flexible material of 0.2~0.5mm. The surface flatness of all-solid-state pouch batteries is not high enough, requiring a flexible material (buffer pad) as a pressure buffer to even out the pressure. The flexible material must be prevented from shifting, which could lead to uneven pressure. The flexible material can be paper or silicone, with a thickness of approximately 0.2~0.5mm. Figure 2 The diagram shows a battery provided in this application, with a flexible buffer pad fixed between the battery's A and B sides and the clamp.

[0069] This application provides a dynamic pressure control clamp system, including: a clamp, a flexible buffer pad, a pressure adjustment module, a time recording unit, and a temperature control unit;

[0070] A pressure regulation module is used to dynamically adjust the pressure applied on the clamp according to the battery's State of Charge (SOC);

[0071] The time recording unit is used to record the duration of each pressure.

[0072] The temperature control unit, integrated with the pressure regulation module, is used to simultaneously detect and adjust the battery temperature during the formation process.

[0073] This application also provides a solid-state battery, which is prepared by any of the formation methods described above.

[0074] This application provides a battery assembly comprising at least two solid-state batteries as described above.

[0075] This application provides an electrical device, including the above-mentioned solid-state battery or battery module, wherein the solid-state battery or battery module serves as the power supply for the electrical device.

[0076] The aforementioned electrical equipment may include at least one of electric vehicles, portable electronic devices, wearable devices, household appliances, and industrial equipment.

[0077] Specifically, electric vehicles may include at least one of electric cars, electric bicycles, and electric scooters; portable electronic devices may include at least one of smartphones, laptops, and tablets; wearable devices may include at least one of smartwatches and fitness trackers; home appliances may include at least one of robotic vacuum cleaners and portable audio equipment; and industrial equipment may include drones.

[0078] The present invention will be further described below through specific embodiments and comparative examples. Unless otherwise specified, the reagents, materials and instruments used below are all conventional reagents, materials and instruments, all of which are commercially available, and the reagents and materials involved can also be synthesized by conventional synthetic methods.

[0079] The following embodiments and comparative examples use the following fixed battery formulations:

[0080] Composite cathode: lithium nickel cobalt manganese oxide, current collector is carbon-coated aluminum foil;

[0081] Composite negative electrode: negative electrode is graphite, current collector is copper foil;

[0082] Solid electrolytes: lithium, phosphorus, sulfur, and chlorine;

[0083] The all-solid-state pouch battery measures 60*80 or 200*70mm and is approximately 7mm thick.

[0084] Preparation method: The positive electrode active material (or positive electrode active material), solid electrolyte, conductive agent and binder are mixed evenly by wet or dry method, and then coated on at least one side of the positive electrode current collector (or negative electrode current collector). After drying (e.g., baking), densification treatment (e.g., rolling) is performed to obtain a composite positive electrode sheet (or composite negative electrode sheet); then the composite positive electrode sheet, solid electrolyte layer and composite negative electrode sheet are arranged in an orderly manner to obtain the electrode core; after the electrode core is placed in the outer shell (casing), isostatic pressing treatment is performed at a pressure of 550 MPa, a temperature of 80℃ and a time of 10 min.

[0085] A 0.5mm silicone buffer layer is placed between the battery surface and the clamp.

[0086] Example 1

[0087] This embodiment performs a formation process on the above-mentioned solid-state battery. The formation method specifically includes the following steps:

[0088] S1. Apply pressure P1 (15MPa) to the battery surface and charge the battery at a constant current rate of C1 (0.1C) until it reaches 30% SOC. Let it rest for 10 minutes.

[0089] S2. Reduce the pressure to P2 (8MPa) and let it stand for 2 hours; the pressure reduction rate v1 is 0.03Mpa / s;

[0090] S3. Under P2 (8MPa) conditions, charge the battery at a constant current rate of C2 (0.3C) until it reaches 80% SOC, and then let it rest for 20 minutes.

[0091] S4. Reduce the pressure to P3 (5MPa) and let it stand for 2 hours; the pressure reduction rate v2 is 0.07Mpa / s;

[0092] S5. Increase the pressure to P4 (15MPa) and let it stand for 2 hours; the pressure increase rate v3 is 1MPa / s.

[0093] S6. Under P4 conditions, discharge the battery at a constant current rate of C3 (0.1C) until it reaches 5% SOC, and then let it stand for 4 hours.

[0094] The battery temperature during the formation process is controlled at 35°C.

[0095] Example 2

[0096] This embodiment performs a formation process on the above-mentioned solid-state battery. The formation method specifically includes the following steps:

[0097] S1. Apply pressure P1 (20MPa) to the battery surface and charge the battery at a constant current rate of C1 (0.1C) until it reaches 20% SOC. Let it rest for 5 minutes.

[0098] S2. Reduce the pressure to P2 (10MPa) and let it stand for 1 hour; the pressure reduction rate v1 is 0.01MPa / s;

[0099] S3. Under P2 (10MPa) conditions, charge the battery at a constant current rate of C2 (0.3C) until it reaches 80% SOC, and then let it rest for 10 minutes.

[0100] S4. Reduce the pressure to P3 (5MPa) and let it stand for 1 hour; the pressure reduction rate v2 is 0.05Mpa / s;

[0101] S5. Increase the pressure to P4 (20MPa) and let it stand for 1 hour; the pressure increase rate v3 is 0.06Mpa / s;

[0102] S6. Under P4 conditions, discharge the battery at a constant current rate of C3 (0.1C) until it reaches 5% SOC, and then let it stand for 2 hours.

[0103] The battery temperature during the formation process is controlled at 35°C.

[0104] Example 3

[0105] This embodiment performs a formation process on the above-mentioned solid-state battery. The formation method specifically includes the following steps:

[0106] S1. Apply pressure P1 (15MPa) to the battery surface and charge the battery at a constant current rate of C1 (0.1C) until it reaches 30% SOC. Let it rest for 10 minutes.

[0107] S2. Reduce the pressure to P2 (8MPa) and let it stand for 2 hours; the pressure reduction rate v1 is 0.03Mpa / s;

[0108] S3. Under P2 (8MPa) conditions, charge the battery at a constant current rate of C2 (0.3C) until it reaches 80% SOC, and then let it rest for 20 minutes.

[0109] S4. Reduce the pressure to P3 (5MPa) and let it stand for 2 hours; the pressure reduction rate v2 is 0.07Mpa / s;

[0110] S5. Increase the pressure to P4 (15MPa) and let it stand for 2 hours; the pressure increase rate v3 is 1MPa / s.

[0111] S6. Under P4 conditions, discharge the battery at a constant current rate of C3 (0.1C) until it reaches 5% SOC, and then let it stand for 4 hours.

[0112] The battery temperature during the formation process is controlled at 65℃.

[0113] Example 4

[0114] This embodiment performs a formation process on the above-mentioned solid-state battery. The formation method specifically includes the following steps:

[0115] S1. Apply pressure P1 (15MPa) to the battery surface and charge the battery at a constant current rate of C1 (0.1C) until it reaches 30% SOC. Let it rest for 10 minutes.

[0116] S2. Reduce the pressure to P2 (8MPa) and let it stand for 2 hours; the pressure reduction rate v1 is 0.03Mpa / s;

[0117] S3. Under P2 (8MPa) conditions, charge the battery at a constant current rate of C2 (0.3C) until it reaches 55% SOC, and then let it rest for 20 minutes.

[0118] S4. Reduce the pressure to P3 (5MPa) and let it stand for 2 hours; the pressure reduction rate v2 is 0.07Mpa / s;

[0119] S5. Increase the pressure to P4 (15MPa) and let it stand for 2 hours; the pressure increase rate v3 is 1MPa / s.

[0120] S6. Under P4 conditions, discharge the battery at a constant current rate of C3 (0.1C) until it reaches 5% SOC, then let it rest for 4 hours to complete one charging cycle.

[0121] Following the above 6 steps, continue with the second charging cycle. In step S3 of the second charging cycle, charge at a constant current to 80% SOC, with the remaining parameters being the same as in the first charging cycle.

[0122] The battery temperature during the formation process is controlled at 35°C.

[0123] Example 5

[0124] The formation process of this application is basically the same as that of the embodiments, except that no buffer pad is provided between the battery and the fixture in this embodiment.

[0125] Comparative Example 1

[0126] This comparative example demonstrates the formation process of the aforementioned solid-state battery. The formation method specifically includes the following steps:

[0127] S1. Apply pressure P1 (15MPa) to the battery surface and charge the battery at a constant current rate of C1 (0.1C) until it reaches 80% SOC. Let it rest for 12 hours.

[0128] S2. Discharge the battery at a constant current rate of C3 (0.1C) until it reaches 5% SOC, then let it rest for 4 hours.

[0129] The temperature during the formation process is controlled at 35℃.

[0130] Comparative Example 2

[0131] This comparative example demonstrates the formation process of the aforementioned solid-state battery. The formation method specifically includes the following steps:

[0132] S1. Apply pressure P1 (15MPa) to the battery surface and charge the battery at a constant current rate of C1 (0.1C) until it reaches 80% SOC. Let it rest for 12 hours.

[0133] S2. Discharge the battery at a constant current rate of C3 (0.1C) until it reaches 5% SOC, then let it rest for 4 hours.

[0134] The battery temperature during the formation process is controlled at 65℃.

[0135] Test case

[0136] The performance of the battery after formation is completed is tested.

[0137] Cyclic performance test: At 35℃, the capacitor was charged at a constant current of 0.5C to 4.25V, then charged at a constant voltage of 4.25V until the current decreased to 0.05C. After resting for 30 minutes, it was discharged at a discharge rate of 1C to 2.5V. This charge-discharge cycle was repeated 200 times. The discharge capacity Q1 at the first cycle and the discharge capacity Q200 at the 200th cycle were measured. Capacity retention rate Q = Q200 / Q1 × 100%.

[0138] Rate performance test: The battery was charged and discharged at 35℃ using a battery charge and discharge tester. The charge and discharge regime was as follows: constant current charging at 0.1C to 4.25V, then constant voltage charging at 4.25V until the current decreased to 0.05C, followed by resting for 30 minutes, and then constant current discharging at 0.33C to 2.5V. The discharge capacity Q was recorded. 0.33c After resting for 30 minutes, charge with a constant current of 0.1C to 4.25V, then switch to a constant voltage of 4.25V and charge until the current decreases to 0.05C. After resting for 30 minutes, discharge with a constant current of 0.5C to 2.5V, and record the discharge capacity Q. 0.5c After resting for 30 minutes, charge with a constant current of 0.1C to 4.25V, then switch to a constant voltage of 4.25V and charge until the current decreases to 0.05C. After resting for 30 minutes, discharge with a constant current of 1C to 2.5V, and record the discharge capacity Q. 1c Capacity retention can be calculated using the following formula: Capacity retention at 1C discharge rate = Q 1c / Q 0.1c ×100%.

[0139] Table 1. Battery Performance

[0140]

[0141] As can be seen from the data in Table 1, the embodiments using the formation process of this application have better capacity retention and rate performance compared to the formation process with fixed pressure.

[0142] Examples 1, 3, and 4 can still undergo formation treatment at 35°C because dynamic pressure control optimizes interfacial contact and reduces interfacial impedance, thereby compensating for the decrease in ionic conductivity caused by the temperature drop.

[0143] All-solid-state lithium-ion batteries are formed at 35~45℃, which is similar to the formation temperature of liquid batteries. This can improve the performance of all-solid-state lithium-ion batteries, greatly reduce the risks of high-temperature formation (battery smoke, fire, explosion, etc.), and reduce production costs.

[0144] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for forming a solid-state battery, characterized in that, Includes the following steps: Apply pressure P1 to the battery surface, charge the battery at a constant current rate of C1 until it reaches a state of charge Q1, and then leave it for time t1. Reduce the pressure to P2 and hold for time t2; Under the conditions described in P2, the battery is charged at a constant current rate of C2 until it reaches a state of charge Q2, and then left to stand for a time t3, where C2 is greater than C1. Reduce the pressure to P3 and hold for t4 time; The pressure is increased to P4, and then held for t5, where P4 is greater than P2. Under the P4 condition, the battery is discharged at a constant current rate of C3 until it reaches the Q3 state of charge, and then left to stand for t6 time to complete one charge-discharge cycle of formation.

2. The method according to claim 1, characterized in that, P1 is 10-20 MPa, P2 is 8-15 MPa, P3 is 5-10 MPa, P4 is 10-20 MPa, and P1 > P2 > P3.

3. The method according to claim 1, characterized in that, C1 is 0.05~0.1C, and C2 is 0.2~0.3C.

4. The method according to any one of claims 1-3, characterized in that, Q1 is 15~30% SOC, Q2 is 55~100% SOC, and Q3 is 0~10% SOC.

5. The method according to any one of claims 1-3, characterized in that, The temperature T1 of the formation process is 35~100℃.

6. The method according to claim 5, characterized in that, The temperature T1 is 35~45℃.

7. The method according to any one of claims 1-3, characterized in that, The t1 is 5~10 min, the t2 is 1~2 h, the t3 is 10~20 min, the t4 is 1~2 h, the t5 is 1~2 h, and the t6 is 2~4 h.

8. The method according to any one of claims 1-3, characterized in that, The rate of voltage reduction to P2 is v1, which is 0.01~0.03 MPa / s; the rate of voltage reduction to P3 is v2, which is 0.05~0.07 MPa / s; and the rate of voltage increase to P4 is v3, which is 0.06~0.1 MPa / s.

9. The method according to any one of claims 1-3, characterized in that, The pressure clamp and the surface of the battery are provided with a flexible buffer pad of 0.2~0.5mm.

10. A solid-state battery, characterized in that, The solid-state battery is prepared by the formation method according to any one of claims 1-9.

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