A charging management method for an all-solid-state battery

Abstract

The present application relates to a kind of charge management methods for all-solid-state battery, periodic pulse charging current is applied to all-solid-state battery, on time period and off time period are both millisecond order;In on time period, pulse charging current makes that the surface area of battery positive active particle is high, the center is low, the particle occurs heterogeneous volume strain, to generate local tensile stress field;In off time period: the chemical potential gradient and the mechanical potential that have been established inside particle drive lithium ion of particle center high concentration area to the surface diffusion of low concentration, make lithium ion concentration inside single particle tend to overall uniform distribution, simultaneously, particle heterogeneous volume strain slows down, make stress relax, reduce stress level;Stress collective relaxation of electrode scale is generated, the stress change of local particle is passed to adjacent particle in microsecond scale, make stress propagate and coherent superposition in whole electrode scale, increase the relaxation level of electrode overall stress.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state battery technology, and more specifically, to a charging management method for improving the fast charging performance of all-solid-state batteries. Background Technology

[0002] All-solid-state batteries (SSBs) are widely considered a key evolutionary direction for next-generation energy storage technology due to their significant potential in energy density and safety. The cathode of an SSB typically consists of active particles, a solid electrolyte, and conductive additives (such as carbon nanotubes or graphene), forming a complex composite particle network. In solid-state systems, the electrolyte itself possesses extremely high elastic modulus, such as oxide electrolytes (e.g., Garnet-type LLZO) or sulfide electrolytes (e.g., Li6PS5Cl). This rigid environment exerts extremely strong physical constraints on the deformation of the active particles. When the active particles undergo lattice contraction during delithiation, the constraint forces generate a highly concentrated stress field at the interface. Currently, relevant research has identified that the main failure path for layered cathode materials (such as NCM811) in SSBs is intergranular cracks along grain boundaries. These cracks not only block the lithium-ion transport path but also expose fresh surfaces, which can induce side reactions in certain chemical systems, further consuming the electrolyte and generating a high-resistivity layer.

[0003] To overcome the above problems, the closest existing technologies in this field mainly include the following categories:

[0004] 1. Surface coating technology (LNO coating layer):

[0005] Coating the surface of NCM particles with nanoscale LiNbO3 (LNO) is a widely used technique. LNO, as a good lithium-ion conductor, can effectively reduce chemical mixing between the cathode and the sulfide electrolyte, and also provides a certain degree of mechanical buffering. Related studies have shown that coated NCM exhibits significantly improved cycle stability in all-solid-state batteries. However, this strategy is inherently static; when faced with extremely high current densities, the LNO coating layer cannot resolve the severe stress accumulation within the particles caused by limited diffusion.

[0006] 2. External physical constraints (stacking pressure):

[0007] Applying external stacking pressure is essential for maintaining solid-state interface contact. Applying pressures from 1 MPa to 100 MPa can effectively suppress interface contact failure during charging. However, high pressure accelerates mechanical damage to the solid electrolyte and increases the added weight and structural complexity of the battery system. Furthermore, the application of macroscopic pressure has limited effect on improving the non-uniform stress distribution at the microscale within the particles.

[0008] The following bottlenecks exist in existing technologies:

[0009] Unable to meet ultra-fast charging demands: At high rates such as 5C, the lithium-ion flux generated in constant current (CC) mode far exceeds the mechanical adaptation speed of the crystal lattice. Existing coating or additive technologies still cause volumetric strain of particle heterogeneity at high current densities, instantaneously reaching the stress limit and triggering "explosive" crack formation;

[0010] Trade-off between energy utilization and stability: In order to maintain stability, existing technologies often have to limit the charging voltage or rate, resulting in the actual usable energy density of the battery being far from the theoretical value, and being significantly reduced at high rates;

[0011] Lack of dynamic repair mechanisms: The generation and accumulation of stress in existing architectures are considered an irreversible degradation process, which will eventually lead to crack growth. Once intergranular fractures form, there is no effective means to "repair" the failed transport path except by applying extremely high external pressure. Summary of the Invention

[0012] The purpose of this invention is to provide a charging management method to improve the fast charging performance of all-solid-state batteries. It proposes a solution to fundamentally improve the limitations of existing technologies in the face of physical and chemical failure problems of all-solid-state batteries under high-rate charging, especially 5C fast charging conditions.

[0013] The objective of this invention is achieved as follows: a charging management method for all-solid-state batteries, comprising:

[0014] A periodic pulse charging current is applied to the all-solid-state battery, wherein each unit pulse consists of an on-time period and an off-time period, both of which are on the order of milliseconds.

[0015] During the conduction period, the pulse charging current causes a high degree of delithiation on the surface of the positive electrode active particles and a low degree of delithiation in the center, resulting in heterogeneous volumetric strain in the particles and thus generating a local tensile stress field.

[0016] During the shutdown period, the application of external current is paused, triggering the following process:

[0017] The established chemical and mechanical potential gradients within the particles drive lithium ions in the high-concentration region at the particle center to diffuse to the low-concentration surface, making the lithium ion concentration within a single particle tend to be uniformly distributed. At the same time, the heterogeneous volumetric strain of the particles is reduced, allowing stress to relax and reducing the stress level.

[0018] This generates collective stress relaxation at the electrode scale. Stress changes in local particles are transmitted to neighboring particles within microseconds, causing stress to propagate and coherently superimpose across the entire electrode scale, thereby increasing the overall stress relaxation level of the electrode.

[0019] Furthermore, the positive electrode of the all-solid-state battery forms a rigid particle network that is in contact with each other and efficiently transmits stress waves. When collective stress relaxation occurs at the electrode scale, the mechanical disturbance caused by local particle volume changes is transformed into an outwardly radiating elastic wave, which sweeps across the entire electrode space within a submicrosecond timescale.

[0020] Furthermore, the frequency of the periodic pulse charging current is between 10Hz and 1000Hz.

[0021] Furthermore, within each pulse of the periodic pulse charging current, a corresponding "charge-relaxation" cycle is formed; through the periodic "charge-relaxation" cycle, the maximum tensile stress inside the electrode is always kept below the material fracture critical value and fluctuates in a "sawtooth" pattern, thus inhibiting the initiation and propagation of cracks.

[0022] The core objective of this invention is to develop a charging management strategy for all-solid-state batteries based on deep coupling of force, electrochemistry, and chemistry. Specific objectives include:

[0023] 1. Achieve stable charging at 5C and above: By dynamically controlling the current input, the peak value of stress accumulation at high rates is controlled below the material fracture limit, thereby unlocking the fast charging performance of high energy density solid-state batteries.

[0024] 2. Construct a "dynamic stress relaxation" window: Utilize millisecond-level OFF time periods to enable lithium ions inside the particles to spontaneously achieve spatial homogenization using their own chemical potential gradient and mechanical potential, thereby eliminating stress concentration.

[0025] 3. Activate the collective stress relief mechanism: Utilize the mechanical continuity of the solid-state battery particle network to promote the diffusion of local stress relaxation to the entire electrode in the form of stress waves, thereby achieving macroscopic stress field optimization.

[0026] 4. Suppressing the initiation and propagation of intergranular cracks: By precisely controlling the time constant (millisecond level), the energy supply to the crack is cut off before it reaches the critical length, thus maintaining the long-term integrity of the grain morphology.

[0027] 5. Improve battery cycle life and safety: By reducing internal structural damage, the risk of increased interface resistance and thermal runaway caused by cracks is reduced, significantly improving the reliability of all-solid-state batteries in real-world application environments.

[0028] The beneficial effects of this invention are as follows:

[0029] 1. Paradigm shift from "static defense" to "dynamic repair": The solution of this invention is a dynamic process control that does not attempt to rigidly resist stress, but allows stress to be "dissipated" through periodic intervals. This "dynamic relaxation" enables the battery to withstand current surges far exceeding its static limits, achieving a leap from passive defense to active self-repair.

[0030] 2. While maintaining fast charging performance, the lifespan is greatly extended: Through millisecond-level pauses, the PC protocol reduces the crack rate in the electrodes while achieving ultra-fast charging;

[0031] 3. Facilitates industrial applications: It only involves optimizing the charging control strategy, without requiring changes to the existing battery material system or production line, resulting in a significant cost reduction. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the solid-state battery pulse charging protocol of the present invention.

[0033] Figure 2 This is a schematic diagram of the propagation state of stress waves between active solid particles in this invention.

[0034] Figure 3 This is a schematic diagram illustrating the stress interaction between active solid particle networks.

[0035] Figure 4 This is a schematic diagram of the PC-5C charging protocol.

[0036] Figure 5 These are simulation results of the force-electric coupling between CC-5C and PC-5C.

[0037] Figure 6 yes Figure 5 A magnified view of a portion of the image.

[0038] Figure 7 This is a schematic diagram of the PC-1C protocol.

[0039] Figure 8 This is a comparison chart of overpotentials during charging using CC-1C and PC-1C protocols.

[0040] Figure 9 This is a comparison chart of battery impedance after 50 cycles under CC-1C and PC-1C protocols.

[0041] Figure 10 This is a comparison chart of the electrochemical cycling performance of the CC-1C and PC-1C protocols.

[0042] Figure 11 This is a comparison chart of the electrochemical cycling performance of the CC-5C and PC-5C protocols.

[0043] Figure 12 These are NCM particle morphology images under the CC-1C protocol, showing the first full charge cycle and after 50 cycles.

[0044] Figure 13 These are NCM particle morphology images under the PC-1C protocol, showing the first full charge cycle and after 50 cycles. Detailed Implementation

[0045] The following will refer to the appendices in the embodiments of the present invention. Figure 1-13 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0046] like Figure 4-13 As shown, the pulse protocol proposed in this invention includes implementation schemes for different power levels, such as PC-1C and PC-5C. This protocol is not simply about switching current, but is based on a deep understanding of stress relaxation dynamics.

[0047] refer to Figure 1 As shown, in the pulse protocol, the period of the current pulse is represented by T, and the formula is:

[0048] .

[0049] Within a complete pulse cycle T, the time during which the charging current is turned on is called the conduction time t. ON The time during which the current is turned off or in a stopped state is called the turn-off time period t. OFF The duty cycle reflects the proportion of the entire pulse cycle that is actually used for charging. The formula for the duty cycle D is defined as:

[0050] ;

[0051] This high-frequency on / off cycle has the following characteristics:

[0052] Conduction time period t ON It is set in the millisecond range, followed by a current-off time period t, which is also in the millisecond range. OFF The millisecond-level time setting matches the time window for electro-mechanical coupling relaxation.

[0053] High instantaneous flux: When the pulse is turned on, extremely high lithium-ion flux is allowed to enter / exit to meet the energy input requirements of fast charging.

[0054] Dynamic relaxation window: When the pulse is turned off, the externally applied electric field disappears, and the system enters a relaxation state driven by the system's built-in chemical and mechanical potentials.

[0055] Therefore, one of the key points of this invention is the concept of precise adaptation of millisecond-level turn-off time constants:

[0056] Technical principle: The millisecond-level time constant is matched with the short-range equilibrium time of lithium ions inside the solid electrode particles and the propagation timescale of the stress field between micro-particles.

[0057] Beneficial effects: If the shutdown time is too short (microseconds), the concentration gradient inside the particles cannot be effectively eliminated; if the shutdown time is too long (seconds or more), it will unnecessarily prolong the total charging time, reduce practicality, and leave the battery in a high-charge state for too long, which may easily lead to calendar aging risks. The millisecond-level selection maximizes the self-healing capability of the solid-state battery system without sacrificing charging speed.

[0058] All of these involve introducing current modulation protocols with frequencies ranging from 10Hz to 1000Hz during solid-state battery charging, particularly those designed for millisecond-level intermittent stress relaxation.

[0059] This invention proposes a novel force-electrochemical coupled repair mechanism, which transforms the traditional unfavorable mechanical failure into a favorable repair mechanism. The physical process is as follows:

[0060] The process of rehoming lithium-ion concentration inside the particles:

[0061] During the conduction time t ON During this stage, due to the anisotropic diffusion coefficient of the layered oxide cathode, lithium is rapidly delithiated from the particle surface region, resulting in anisotropic contractile strain and thus local tensile stress.

[0062] During the shutdown period t OFF During this stage, according to Fick's second law and the stress-assisted diffusion model, the built-in concentration gradient chemical and mechanical potentials within the particle jointly drive the diffusion of excess lithium ions from the particle center to the lithium-poor surface. By periodically removing the external current field, t... ON The battery management logic that uses the accumulated mechanical and chemical potential energy to drive the solute (lithium ions) to redistribute in a uniform manner.

[0063] This invention proposes a stress-driven lithium-ion homogenization (reverse repair driven) concept, turning waste into treasure by transforming the driving force leading to degradation into the driving force for repair. During the pulse pause, the residual stress gradient is used as an additional driving force to accelerate the return of lithium ions to the particle surface, mitigating heterogeneous volumetric strain, thereby pre-reducing the high-stress state of the surface before the next pulse begins. This mechanism achieves true "in-situ repair," enabling particles to operate under consistently low stress and high dynamic conditions.

[0064] Stress wave propagation in solid particle networks:

[0065] As shown in Figures 2 and 3, this invention reveals the unique "stress radiation" effect of all-solid-state batteries by constructing a transient elastic dynamics model at the particle-electrode scale. Unlike traditional lithium-ion batteries, the positive electrode of an all-solid-state battery is a rigid network of interconnected particles, and stress changes in local particles are transmitted to neighboring particles within microseconds (μs) through phonon transmission or elastic waves.

[0066] Extremely rapid propagation is possible: the continuous rigid network of positive electrode active particles provides an efficient transmission path for stress waves. The mechanical disturbances caused by local particle volume changes are rapidly converted into outward-radiating elastic waves, which sweep across the entire electrode space within a sub-microsecond timescale.

[0067] Wave velocity measurement: Simulation analysis shows that the propagation velocity of stress waves in the NCM811 / LPSC composite cathode is as high as 4250 m / s (e.g., Figure 3 (As shown).

[0068] A quantitative model for collective stress fluctuations is provided:

[0069] To quantitatively assess the impact of collective stress generated by the particle network, this invention introduces a mathematical model:

[0070] Stress attenuation law: Stress caused by a single particle It decays with increasing radial distance r, following the mathematical formula below:

[0071] ;

[0072] in, The initial stress generated by the source particle, characteristic length = 10.25 μm (for a uniform NCM811|LPSC system) characterizes the dissipation rate of stress waves in the composite cathode.

[0073] Collective Stress Wave Superposition: In electrochemical cycling, a large number of active particles undergo synchronous volume changes, acting as independent stress wave sources. Due to the randomness of their spatial distribution and multiple scattering effects, the stress waves reaching the target particles experience random phase loss. Collective stress wave superposition is derived by performing root-mean-square superposition on the interactions. The integral formula:

[0074] ;

[0075] Parameter description:

[0076] D: Electrode diameter (1 cm in the example);

[0077] : Average radius of active particles;

[0078] L: Electrode thickness (300 μm in the example);

[0079] : Volume density of particles;

[0080] P: Activation probability, representing the proportion of particles that experience transient stress changes per unit time.

[0081] Simulations and formula calculations together demonstrate that macroscopic collective interactions induce significant dynamic stress fluctuations. For example, when the activation probability P = 10... -6 At that time, the collective dynamic stress fluctuated significantly between 0.71 and 1.29 times that of the individual particle stress. This collective effect caused by "stress radiation" is a potential cause of cascaded mechanical failure. This invention uses pulse protocol to control the relaxation time of the shutdown period and utilizes this fluctuation mechanism to achieve effective stress release and optimized distribution. This is the physical basis for high-rate cycle repair of all-solid-state batteries.

[0082] This invention identifies and quantifies the "collective stress relaxation" phenomenon in solid particle networks. By utilizing the mechanical continuity of solid systems, it triggers synchronous stress response across the entire electrode range through discrete pulse signals, thereby achieving macroscopic stress relaxation at the electrode scale.

[0083] The technical solution utilizes active particles in solid-state batteries as stress change sources and particle networks as stress propagation media to generate stress waves with collective repair characteristics through pulsed current, thereby suppressing electrode cracking. This mechanism enables the electrode to distribute local loads through "collective breathing" when subjected to high-rate current impacts, greatly improving the electrode's fracture toughness.

[0084] like Figure 4-13 As shown, the present invention provides some application examples.

[0085] Figure 4-6 Force-electric coupling simulation is provided:

[0086] Figure 4 The PC-5C protocol is provided, such as Figure 5 The results of the PC-5C electromechanical coupling simulation show the evolution of the maximum tensile stress of the electrode during the charging process.

[0087] To facilitate the display of details, Figure 6 for Figure 5 The enlarged view shows the evolution of the maximum tensile stress of the electrode during the charging process, which can be seen from the PC-5C electromechanical coupling simulation results.

[0088] By establishing a force-electric coupling phase-field model, the evolution of the maximum tensile stress inside the electrode under the PC-5C protocol was simulated.

[0089] Constant current (CC-5C) control group: The stress increases linearly and continuously with the charging progress, and the stress growth rate accelerates with the charging time, which easily breaks through the critical failure point of fracture, indicating the generation of large-scale cracks.

[0090] Pulsed (PC-5C) experimental group: Stress evolution exhibits a significant "sawtooth" characteristic. During each millisecond-level pulse shutdown, the maximum tensile stress drops sharply. (See enlarged inset). Figure 6 It can be clearly observed that this dynamic relaxation ensures that the stress is always kept below the safety threshold, thus achieving effective suppression of cracks.

[0091] Figure 8 , 9 A comparison of impedance and overpotential is provided:

[0092] like Figure 7 The PC-1C protocol is shown, such as Figure 8 The diagram shows a comparison of overpotentials during charging using the CC-1C and PC-1C protocols; this embodiment compares the CC-1C and PC-1C protocols. Experimental results show:

[0093] Overpotential: The average charging overpotential under the PC protocol is significantly lower than that under the CC protocol, indicating that pulse pause effectively reduces surface polarization and improves interface dynamics.

[0094] Figure 9 A comparison of battery impedance after 50 cycles under CC-1C and PC-1C protocols is provided:

[0095] Impedance evolution: After 50 cycles, the battery EIS spectrum under the CC protocol showed a significant increase in charge transfer impedance, while the battery impedance under the PC protocol showed a very small increase, proving that the mechanical integrity of the interface was well preserved.

[0096] Figure 10 Cyclic stability analysis is provided:

[0097] In both 1C (Figure 10) and 5C (Figure 11) cycle tests, the PC protocol demonstrated a strong advantage. Especially in the 5C fast charging environment, traditional protocols experienced severe performance degradation within less than 20 cycles, while the PC-5C protocol was still able to maintain stable capacity output, with a capacity retention rate improved several times.

[0098] Figure 10 A comparison of electrochemical cycling performance under CC-5C and PC-5C protocols is provided:

[0099] Figures 11 and 12 provide structural stability analysis; in Figure 11 In the image, the NCM particle morphology (CT characterization rendering image) under the CC-1C protocol at full charge in the first cycle and after 50 cycles; Figure 12 In the image, the NCM particle morphology in the first full charge state and after 50 cycles under the PC-1C protocol (CT characterization rendering image).

[0100] Under the CC-1C protocol, after the first full charge cycle and 50 cycles, the NCM particles began to crack, and after 50 cycles, the cracking became severe, exhibiting fibrous through-cracks.

[0101] Under the CC-1C protocol, after the first full charge cycle and 50 cycles, the NCM particle structure remained relatively intact, with only a few pores growing.

[0102] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. In this invention, it should also be noted that the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, an integrally formed connection, a mechanical connection, or an indirect connection through intermediate connecting parts. The specific meaning of the terms in this utility model can be understood according to the specific circumstances.

[0103] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0104] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A charging management method for all-solid-state batteries, characterized in that, include: A periodic pulse charging current is applied to the all-solid-state battery, wherein each unit pulse consists of an on-time period and an off-time period, both of which are on the order of milliseconds. During the conduction period, the pulse charging current causes a high degree of delithiation on the surface of the positive electrode active particles and a low degree of delithiation in the center, resulting in heterogeneous volumetric strain in the particles and thus generating a local tensile stress field. During the shutdown period, the application of external current is paused, triggering the following process: The established chemical and mechanical potential gradients within the particles drive lithium ions in the high-concentration region at the particle center to diffuse to the low-concentration surface, making the lithium ion concentration within a single particle tend to be uniformly distributed. At the same time, the heterogeneous volumetric strain of the particles is reduced, allowing stress to relax and reducing the stress level. This generates collective stress relaxation at the electrode scale. Stress changes in local particles are transmitted to neighboring particles within microseconds, causing stress to propagate and coherently superimpose across the entire electrode scale, thereby increasing the overall stress relaxation level of the electrode.

2. The charging management method for all-solid-state batteries according to claim 1, characterized in that, The positive electrode of an all-solid-state battery forms a rigid particle network that is in contact with each other and efficiently transmits stress waves. When collective stress relaxation occurs at the electrode scale, the mechanical disturbance caused by local particle volume changes is transformed into an outwardly radiating elastic wave, which sweeps across the entire electrode space within a submicrosecond timescale.

3. The charging management method for all-solid-state batteries according to claim 2, characterized in that, The frequency of the periodic pulse charging current is between 10 Hz and 1000 Hz.

4. The charging management method for all-solid-state batteries according to claim 2, characterized in that, During each pulse of the periodic pulse charging current, a corresponding "charge-relaxation" cycle is formed. Through the periodic "charge-relaxation" cycle, the maximum tensile stress inside the electrode is always kept below the material fracture critical value and fluctuates in a "sawtooth" pattern, thus inhibiting the initiation and propagation of cracks.

5. The charging management method for all-solid-state batteries according to claim 4, characterized in that, The millisecond-level time settings for the on and off periods are matched to the time window of the electro-mechanical coupling relaxation.

6. The charging management method for all-solid-state batteries according to claim 4, characterized in that, The period of a current pulse is defined as T, and the formula is: ； Within a complete pulse cycle T, the time during which the charging current is turned on is called the conduction time t. ON The time during which the current is turned off or in a stopped state is called the turn-off time period t. OFF .

7. A charging management method for all-solid-state batteries according to claim 6, characterized in that, Define the duty cycle as D, and the formula is: ； In the formula, during the conduction time t ON In this process, extremely high lithium-ion flux enters / exits to meet the energy input requirements of fast charging; During the shutdown period t OFF During the dynamic relaxation window, the externally applied force field disappears, and the system enters a relaxation state driven by chemical and mechanical potentials.

8. The charging management method for all-solid-state batteries according to claim 2, characterized in that, Stress caused by a single particle It decays with increasing radial distance r, following the mathematical formula below: ； in, The initial stress generated by the source particles, The characteristic length represents the dissipation rate of the stress wave in the composite cathode.

9. A charging management method for all-solid-state batteries according to claim 8, characterized in that, The collective stress fluctuation was obtained by performing root-mean-square superposition on the interactions of the active particles. The integral formula: ； Parameter description: D: Electrode diameter; : Average radius of active particles; L: Electrode thickness; : Volume density of particles; P: Activation probability, representing the proportion of particles that experience transient stress changes per unit time.

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