A detection method based on sulfur fixation performance of lithium-sulfur battery positive electrode material

Abstract

The application relates to the technical field of lithium-sulfur battery detection, in particular to a detection method based on the sulfur fixation performance of a lithium-sulfur battery positive electrode material, which comprises the following steps: obtaining voltage signal sequences and current signal sequences of a lithium-sulfur battery at multiple sampling time points in a preset charge-discharge cycle; injecting the voltage signal sequences and the current signal sequences into a sulfur fixation performance evolution field, constructing a dynamic representation topology that deforms with the cycle state of the battery, generating a sulfur fixation evolution trace, capturing a trace morphology transition event, extracting a sulfur fixation abnormal feature, using the feature to drive a sulfur fixation performance analyzer based on field evolution feedback to output a calibration instruction, calibrating the deformation of the dynamic representation topology, and generating a sulfur fixation performance quantization result based on the new trace distribution after calibration. The method can realize dynamic monitoring and accurate quantization of the sulfur fixation performance, and improves the continuity and accuracy of detection.

Description

Technical Field

[0001] This invention relates to the field of lithium-sulfur battery testing technology, and in particular to a testing method based on the sulfur fixation performance of lithium-sulfur battery cathode materials. Background Technology

[0002] Currently, the sulfur fixation performance of lithium-sulfur battery cathode materials is mostly tested by analyzing static electrochemical signals after charge-discharge cycles. By monitoring the voltage and current change trends during the cycle process and combining the physical characterization of the material, the sulfur fixation effect can be judged. A common method is to perform electrochemical tests on the cathode material at a fixed number of cycles, extract characteristic parameters, and compare them with standard values ​​to evaluate the sulfur fixation performance.

[0003] These methods can only acquire static signals at specific moments and cannot capture the dynamic evolution of sulfur fixation performance with charge-discharge cycles. They are difficult to accurately identify abnormal changes in the sulfur fixation process. Furthermore, traditional detection methods have not constructed a characterization system that matches the sulfur fixation evolution. The analysis of signals is only superficial and cannot establish a direct correlation between electrochemical signals and dynamic changes in sulfur fixation performance. This results in lag and bias in the detection results and cannot accurately reflect the true evolution of the sulfur fixation performance of the cathode material.

[0004] Existing technologies cannot achieve dynamic real-time monitoring of sulfur fixation performance, making it difficult to accurately capture abnormal characteristics during the sulfur fixation process. Furthermore, they lack effective feedback calibration mechanisms and cannot correct signal analysis deviations during the detection process. This results in insufficient accuracy of the quantitative results of sulfur fixation performance and fails to meet the demand for accurate detection of sulfur fixation performance in lithium-sulfur battery cathode materials. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for detecting the sulfur fixation performance of lithium-sulfur battery cathode materials.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for detecting the sulfur fixation performance of lithium-sulfur battery cathode materials, comprising: The electrochemical signals of the cathode material of a lithium-sulfur battery at multiple sampling times during a preset charge-discharge cycle test are obtained. The electrochemical signals include voltage signal sequences and current signal sequences. The electrochemical signal is injected into the sulfur fixation performance evolution field for dynamic analysis. A dynamic characterization topology that deforms with the battery cycle state is constructed in the sulfur fixation performance evolution field. Sulfur fixation evolution traces are generated between the nodes of the dynamic characterization topology based on the voltage signal sequence and the current signal sequence. The morphological transition events of the sulfur fixation evolution trajectory are monitored and captured. When the local morphological change rate of the sulfur fixation evolution trajectory exceeds the transition detection threshold, the signal segment of the sulfur fixation evolution trajectory and its corresponding dynamic characterization topological region are extracted to form sulfur fixation anomaly features. Using the sulfur fixation anomaly features as input, a sulfur fixation performance analyzer based on field evolution feedback is driven. The sulfur fixation performance analyzer based on field evolution feedback outputs field calibration evolution instructions based on the distortion features of signal segments within the sulfur fixation anomaly features and the configuration distribution of the dynamic characterization topology region. According to the field calibration evolution command, a corresponding calibration deformation is applied to the dynamic characterization topology in the sulfur fixation performance evolution field, and the dynamic characterization topology after calibration deformation generates a new sulfur fixation evolution trace distribution. Based on the new sulfur fixation evolution trajectory distribution, quantitative results of sulfur fixation performance for lithium-sulfur battery cathode materials are generated.

[0007] As a further aspect of the present invention, the step of injecting the electrochemical signal into the sulfur fixation performance evolution field for dynamic analysis, and constructing a dynamic characterization topology in the sulfur fixation performance evolution field that deforms with changes in battery cycling state, includes: The instantaneous values ​​of sulfur embedding capacity and voltage hysteresis are calculated at each sampling time based on the voltage signal sequence and the current signal sequence. A two-dimensional sulfur fixation performance evolution field is constructed with the instantaneous value of sulfur embedding capacity as the horizontal axis and the instantaneous value of voltage hysteresis as the vertical axis, and the sulfur fixation state point at each sampling time is plotted in the two-dimensional sulfur fixation performance evolution field. Connect the sulfur fixation state points at adjacent sampling times in the two-dimensional sulfur fixation performance evolution field to form a sulfur fixation evolution trajectory line; Based on the spatial distribution density of the sulfur fixation evolution trajectory, a non-uniform polygonal mesh is automatically generated in the two-dimensional sulfur fixation performance evolution field to cover the sulfur fixation evolution trajectory. The vertex density of the polygonal mesh is positively correlated with the local morphological change rate of the sulfur fixation evolution trajectory. The polygonal mesh is a dynamic topology that adjusts its vertex positions and connection relationships as the sulfur fixation state points change.

[0008] As a further aspect of the present invention, the step of generating sulfur fixation evolution traces between nodes of the dynamically characterized topology based on voltage signal sequences and current signal sequences includes: For each polygonal mesh cell representing the dynamic topology, calculate the evolution gradient vector of the instantaneous values ​​of the sulfur embedding capacity and voltage hysteresis corresponding to its vertices; The evolution gradient vectors of multiple vertices within each polygonal grid cell are weighted and fused to obtain the sulfur fixation evolution direction vector of that polygonal grid cell. Along the sulfur fixation evolution direction vector field, a trace is drawn on the dynamic characterization topology from the high sulfur intercalation capacity region to the low sulfur intercalation capacity region. The trace is the sulfur fixation evolution trace that characterizes the real-time evolution path and intensity of sulfur fixation performance.

[0009] As a further aspect of the present invention, the monitoring and capturing of the morphological transition events of the sulfur fixation evolution trajectory includes: The local morphological change rate is calculated along each sulfur fixation evolution trajectory with a fixed step size to form a sequence of change rates of sulfur fixation evolution trajectories; Apply the sliding difference detection operation to the rate of change sequence to detect the moment when the difference value in the rate of change sequence exceeds the transition detection threshold, and mark it as the moment when the morphological transition event occurs; Back to the time of occurrence, extract the sulfur fixation evolution trajectory segment within the preset observation window before and after the time of occurrence, and record the set of polygonal grid cells in the dynamic characterization topology through which the sulfur fixation evolution trajectory segment passes. The sulfur fixation evolution trajectory segment and the set of polygonal grid cells together constitute the sulfur fixation anomaly feature.

[0010] As a further aspect of the present invention, the step of using the sulfur fixation anomaly characteristics as input to drive a sulfur fixation performance analyzer based on field evolution feedback includes: The signal segments within the sulfur fixation anomaly feature are subjected to joint time-frequency analysis to extract the dominant distortion component and distortion energy distribution in their time spectrum as signal distortion features. The dynamic topological region within the sulfur fixation anomaly is analyzed, and the rate of change of geometric parameters and angular offset of all polygonal mesh elements within this region are calculated as topological configuration distribution characteristics. The signal distortion features and topological configuration distribution features are input into a pre-trained evolutionary decision network. The evolutionary decision network outputs instructions to apply expansion, contraction or rotation deformation to the target region that dynamically represents the topology, as well as the deformation amplitude and direction corresponding to each deformation instruction, which together constitute the field calibration evolution instructions.

[0011] As a further aspect of the present invention, the step of applying a corresponding calibration deformation to the dynamic characterization topology in the sulfur fixation performance evolution field according to the field calibration evolution command includes: In the two-dimensional sulfur fixation performance evolution field, the target region specified by the field calibration evolution command is located, and the target region is identified by a set of polygonal mesh cells; According to the deformation type and deformation magnitude in the field calibration evolution command, the vertex coordinates of all polygonal mesh elements in the target area are updated collaboratively. After updating the vertex coordinates, the connectivity and geometric properties of all affected polygon mesh cells are recalculated and updated to complete the construction of the dynamic representation topology after calibration deformation.

[0012] As a further aspect of the present invention, the step of generating quantitative results of sulfur fixation performance for lithium-sulfur battery cathode materials based on the new sulfur fixation evolution trace distribution includes: Stable sulfur fixation channels were identified in the new sulfur fixation evolution trajectory distribution. These stable sulfur fixation channels were defined by the morphological change rate of the sulfur fixation evolution trajectory being consistently below a stability threshold. The stable sulfur fixation channel is mapped back to the electrochemical signal space and converted into steady-state voltage reference command and sulfur fixation state command. Simultaneously, polysulfide shuttle noise stripping is performed on the electrochemical signal to separate the main sulfur fixation mode and the residual shuttle oscillation mode; The steady-state sulfur fixation signal defined by the steady-state voltage reference command and the sulfur fixation state command is fused with the residual shuttle oscillation mode to synthesize a comprehensive sulfur fixation performance indicator signal. Based on the comprehensive sulfur fixation performance indicator signal, quantitative results of sulfur fixation performance for lithium-sulfur battery cathode materials are generated.

[0013] As a further aspect of the present invention, identifying stable sulfur fixation channels in the new sulfur fixation evolution trajectory distribution includes: The sulfur solidification evolution trace is regenerated on the dynamically characterized topology after calibration deformation; The morphological change rate of newly generated sulfur fixation evolution traces is observed within a preset observation period. If the maximum morphological change rate of a certain sulfur fixation evolution trace is consistently lower than the stability threshold throughout the entire observation period, then the sulfur fixation evolution trace is determined to be a stable sulfur fixation channel. Record the starting coordinates, ending coordinates, and grid cell sequence of all stable sulfur fixation channels in the two-dimensional sulfur fixation performance evolution field.

[0014] As a further aspect of the present invention, the step of mapping the stable sulfur fixation channel back to the electrochemical signal space and converting it into a steady-state voltage reference command and a sulfur fixation state command includes: For each stable sulfur fixation channel, the average sulfur intercalation capacity and average voltage hysteresis value of the stable sulfur fixation channel in the two-dimensional sulfur fixation performance evolution field are calculated based on its starting point coordinates and ending point coordinates. By using a pre-defined electrochemical mapping relationship, the average sulfur intercalation capacity value and the average voltage hysteresis value are converted into the steady-state voltage reference command and the sulfur fixation state command characterizing the sulfur fixation capability under the corresponding cycle conditions.

[0015] As a further aspect of the present invention, the step of stripping polysulfide shuttle noise from the electrochemical signal to separate the main sulfur-fixing mode and the residual shuttle oscillation mode includes: Adaptive noise-complete empirical mode decomposition is applied to voltage signal sequences and current signal sequences to obtain a series of intrinsic mode components. Based on the instantaneous frequency of the intrinsic mode components, intrinsic mode components whose instantaneous frequency is consistent with the main frequency of the electrochemical reaction are selected, and these components are reconstructed into the main sulfur fixation mode. Subtracting the main sulfur fixation mode from the original electrochemical signal, the remaining waveform components are the residual shuttle oscillation modes; The process of fusing the steady-state sulfur fixation signal defined by the steady-state voltage reference command and the sulfur fixation state command with the residual shuttle oscillation mode to synthesize a comprehensive sulfur fixation performance indicator signal includes: Based on the steady-state voltage reference command and the sulfur fixation state command, a standard electrochemical reference waveform is generated as the steady-state sulfur fixation signal; The steady-state sulfur fixation signal and the residual shuttle oscillation mode are superimposed in the time domain to obtain a preliminary performance indication signal; The preliminary performance indication signal is normalized and smoothed to ensure that its value is within the preset quantization range and the waveform is continuous. The processed signal is the comprehensive sulfur fixation performance indication signal used to quantify sulfur fixation performance.

[0016] Compared with the prior art, the advantages and positive effects of the present invention are as follows: By injecting the voltage and current signal sequences of lithium-sulfur batteries during preset charge-discharge cycles into the sulfur fixation performance evolution field, a dynamic characterization topology that deforms with changes in battery cycle state is constructed. Based on the two types of signal sequences, sulfur fixation evolution traces are generated between the nodes of this dynamic characterization topology. This breaks through the limitations of traditional static signal detection and can capture the dynamic evolution process of sulfur fixation performance with charge-discharge cycles in real time. It establishes a direct correlation between electrochemical signals and the evolution of sulfur fixation performance, accurately presenting subtle changes in the sulfur fixation process. This avoids the problem that traditional detection can only obtain static signals at specific moments and cannot reflect the dynamic changes in sulfur fixation performance, making the monitoring of sulfur fixation performance more continuous and comprehensive.

[0017] Using the signal fragments extracted after capturing the morphological transition events of sulfur fixation evolution traces and the sulfur fixation anomalies formed by the corresponding dynamic characterization topology regions as inputs, the sulfur fixation performance analyzer based on field evolution feedback is driven to output field calibration evolution commands. The dynamic characterization topology within the sulfur fixation performance evolution field is calibrated and deformed. Then, based on the new distribution of sulfur fixation evolution traces after deformation, the quantitative results of sulfur fixation performance are generated. Through the feedback calibration mechanism, the deviation in the signal analysis process is corrected, making up for the lack of effective calibration methods in traditional detection. This makes the extraction of sulfur fixation anomalies more accurate, and thus makes the quantitative results of sulfur fixation performance more consistent with the true state of sulfur fixation performance of cathode materials, avoiding the problems of lag and bias in traditional detection results. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for detecting the sulfur fixation performance of lithium-sulfur battery cathode materials according to the present invention; Figure 2 A flowchart for constructing a dynamic representation topology; Figure 3A flowchart for monitoring and capturing morphological transition events; Figure 4 A diagram showing the relationship between sulfur fixation state commands and steady-state voltage reference commands; Figure 5 This is a comparison graph of the voltage of a lithium-sulfur battery before and after cycling. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] In the description of this invention, it should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the 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, and therefore should not be construed as a limitation of the invention. Furthermore, in the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0021] See Figure 1 The method acquires electrochemical signals of the cathode material at multiple sampling moments during a preset charge-discharge cycle test of a lithium-sulfur battery. These electrochemical signals include voltage and current signal sequences. The electrochemical signals are injected into a sulfur fixation performance evolution field for dynamic analysis. A dynamic characterization topology, deforming with changes in battery cycle state, is constructed within this field. Sulfur fixation evolution traces are generated between nodes in the dynamic characterization topology based on the voltage and current signal sequences. Morphological transition events of the sulfur fixation evolution traces are monitored and captured. When the local morphological change rate of the sulfur fixation evolution trace exceeds a transition detection threshold, the signal segment of that trace and its corresponding dynamic characterization topology region are extracted, forming a sulfur fixation anomaly feature. Using this anomaly feature as input, a sulfur fixation performance analyzer based on field evolution feedback is driven. This analyzer outputs field calibration evolution commands based on the distortion characteristics of the signal segments within the sulfur fixation anomaly feature and the configuration distribution of the dynamic characterization topology region. According to the field calibration evolution command, a corresponding calibration deformation is applied to the dynamic characterization topology in the sulfur fixation performance evolution field. The dynamically characterization topology after calibration deformation generates a new sulfur fixation evolution trace distribution. Based on the new sulfur fixation evolution trace distribution, quantitative results of the sulfur fixation performance of lithium-sulfur battery cathode materials are generated.

[0022] In one embodiment of the present invention, electrochemical signals are injected into the sulfur fixation performance evolution field for dynamic analysis. A dynamic characterization topology that deforms with changes in battery cycling state is constructed within this field. The process is described in [reference needed]. Figure 2 The instantaneous values ​​of sulfur embedding capacity and voltage hysteresis at each sampling moment are calculated based on the voltage and current signal sequences. A two-dimensional sulfur fixation performance evolution field is constructed with the instantaneous value of sulfur embedding capacity as the horizontal axis and the instantaneous value of voltage hysteresis as the vertical axis, and the sulfur fixation state point at each sampling moment is plotted in the two-dimensional sulfur fixation performance evolution field. The sulfur fixation state points at adjacent sampling moments in the two-dimensional sulfur fixation performance evolution field are connected to form a sulfur fixation evolution trajectory line. Based on the spatial distribution density of the sulfur fixation evolution trajectory line, a non-uniform polygonal grid is automatically generated in the two-dimensional sulfur fixation performance evolution field to cover the sulfur fixation evolution trajectory line. The vertex density of this polygonal grid is positively correlated with the local morphological change rate of the sulfur fixation evolution trajectory line. This polygonal grid is the dynamic representation topology that adjusts its vertex positions and connection relationships as the sulfur fixation state points change. Sulfur fixation evolution trajectories are generated between the nodes of the dynamic representation topology based on the voltage and current signal sequences. The process involves calculating the evolution gradient vector of the instantaneous value of sulfur embedding capacity and the instantaneous value of voltage hysteresis corresponding to the vertex of each polygonal grid unit of the dynamic representation topology. The evolution gradient vectors of multiple vertices within each polygonal grid cell are weighted and fused to obtain the sulfur fixation evolution direction vector of that polygonal grid cell. Along the sulfur fixation evolution direction vector field, a trace is drawn on the dynamic topology from the high sulfur intercalation capacity region to the low sulfur intercalation capacity region. This trace is the sulfur fixation evolution trace that characterizes the real-time evolution path and intensity of sulfur fixation performance.

[0023] In practical implementation, the instantaneous values ​​of sulfur embedding capacity and voltage lag at each sampling moment are calculated based on the voltage and current signal sequences. The instantaneous value of sulfur embedding capacity is obtained by numerically integrating the current signal sequence within a time window, and the instantaneous value of voltage lag is obtained by calculating the algebraic difference between the voltage value at each sampling point in the voltage signal sequence and the preset reference voltage value. A two-dimensional sulfur fixation performance evolution field is constructed with the instantaneous value of sulfur embedding capacity on the horizontal axis and the instantaneous value of voltage lag on the vertical axis. The sulfur fixation state point at each sampling moment is plotted in the two-dimensional sulfur fixation performance evolution field, and the sulfur fixation points at adjacent sampling moments in the two-dimensional sulfur fixation performance evolution field are connected. State points form sulfur fixation evolution trajectory lines. Based on the spatial distribution density of these trajectory lines, a non-uniform polygonal mesh is automatically generated in the two-dimensional sulfur fixation performance evolution field to cover them. The vertex density of the polygonal mesh is positively correlated with the local morphological change rate of the sulfur fixation evolution trajectory lines. The polygonal mesh is a dynamic topology representing the adjustment of vertex positions and connections as sulfur fixation state points change. The local morphological change rate is obtained by calculating the rate of change of the angle formed by three consecutive sulfur fixation state points on the sulfur fixation evolution trajectory line. When the local morphological change rate increases, more polygonal mesh vertices are inserted around the corresponding sulfur fixation evolution trajectory line segment. The instantaneous sulfur embedding capacity value represents the real-time capacity of sulfur species already embedded within the cathode material at the corresponding sampling time; the instantaneous voltage hysteresis value represents the deviation of the actual test voltage from the theoretical equilibrium voltage under this electrochemical state. The instantaneous sulfur embedding capacity value is obtained by time integration of the acquired current signal, calculated using the following formula:

[0024] In the formula, This represents the instantaneous value of the sulfur intercalation capacity. This marks the start time of the charge / discharge test. This is the current sampling time; for Battery current obtained by sampling at any time.

[0025] Formula for calculating the instantaneous value of voltage hysteresis:

[0026] In the formula, This represents the instantaneous value of voltage hysteresis. The measured voltage of the battery obtained through sampling; This is the theoretical equilibrium voltage of the lithium-sulfur battery cathode corresponding to this sulfur intercalation capacity state, obtained by looking up the standard lithium-sulfur cathode electrochemical equilibrium curve.

[0027] A sulfur fixation state point is a coordinate point in the two-dimensional sulfur fixation performance evolution field used to characterize the real-time sulfur fixation state of the battery cathode at a certain sampling time. At each sampling time, the instantaneous value of the sulfur embedding capacity calculated at that time is used as the abscissa, and the instantaneous value of the voltage hysteresis calculated at that time is used as the ordinate. This set of coordinates generates a sulfur fixation state point. All sulfur fixation state points corresponding to all sampling times are plotted in the coordinate system of the two-dimensional sulfur fixation performance evolution field.

[0028] In some embodiments, for each polygonal mesh cell representing the dynamic topology, the evolution gradient vector of the instantaneous values ​​of sulfur embedding capacity and voltage hysteresis corresponding to the vertex of the polygonal mesh cell is calculated. The evolution gradient vector represents the changing trend of the sulfur fixation state at the vertex over time. The formula for calculating the evolution gradient vector is expressed as follows:

[0029] Where: symbol Represents vertices The evolution gradient vector, symbol Indicates the instantaneous value of sulfur intercalation capacity, symbol Represents the instantaneous value of voltage lag, symbol Indicates the sampling time, symbol The sampling time interval is represented by the weighted fusion of the evolution gradient vectors of multiple vertices within each polygonal grid cell to obtain the sulfur fixation evolution direction vector of the polygonal grid cell. During the weighted fusion process, the weight coefficient of each vertex is proportional to the reciprocal of the Euclidean distance from that vertex to the geometric center of the polygonal grid cell. Along the sulfur fixation evolution direction vector field, a trace is drawn on the dynamic topology from the high sulfur embedding capacity region to the low sulfur embedding capacity region. The high sulfur embedding capacity region is composed of polygonal grid cells whose instantaneous sulfur embedding capacity is greater than the average value of the entire field, and the low sulfur embedding capacity region is composed of polygonal grid cells whose instantaneous sulfur embedding capacity is less than the average value of the entire field. The trace is the sulfur fixation evolution trace that characterizes the real-time evolution path and intensity of sulfur fixation performance. Data comparison reveals differences in the spatial distribution of sulfur fixation evolution trajectories at different cycle stages. For example, in the early stages of a cycle, the sulfur fixation evolution trajectory may be concentrated in a specific region of the two-dimensional sulfur fixation performance evolution field, while in the later stages, it may exhibit divergent or intersecting patterns. This difference directly affects the vertex distribution density of the polygonal mesh in the dynamic representation topology. Changes in the vertex distribution density of the polygonal mesh further affect the calculation of the sulfur fixation evolution direction vector, thereby altering the direction and shape of the sulfur fixation evolution trajectory. In practical implementation, the polygonal mesh is generated using an incremental Delaunay triangulation algorithm. The algorithm uses sulfur fixation state points as the initial point set and dynamically inserts new vertices based on the local morphological change rate of the sulfur fixation evolution trajectory. The insertion frequency of vertices increases in regions with high local morphological change rates, ensuring that the non-uniformity of the dynamic representation topology accurately matches the geometric characteristics of the sulfur fixation evolution trajectory. Optionally, the sulfur fixation evolution trajectory is plotted using a numerical integration method. Starting from a polygonal grid cell within a high sulfur intercalation capacity region, the sulfur fixation evolution direction vector of that cell is used as the initial direction. The next location point is iteratively calculated with a fixed step size. The current direction is determined by the polygonal grid cell in which the location point falls, until the location point enters a low sulfur intercalation capacity region or reaches the boundary of the two-dimensional sulfur fixation performance evolution field. The line connecting all iterative location points forms a complete sulfur fixation evolution trajectory. In some embodiments, the sulfur fixation evolution direction vector of the polygonal grid cell is recalculated after each dynamic characterization topology update to ensure that the sulfur fixation evolution trajectory reflects the latest battery cycle state. Data comparison is also achieved by comparing the total length and number of branches of the sulfur fixation evolution trajectory generated by the same battery at different cycle numbers. The total length of the sulfur fixation evolution trajectory reflects the overall path of sulfur fixation performance evolution, while the number of branches reflects the complexity of the evolution path.

[0030] In one embodiment of the present invention, see [reference] Figure 3The process involves calculating the local morphological change rate along each sulfur fixation evolution trajectory with a fixed step size, forming a sequence of change rates for the sulfur fixation evolution trajectory. A sliding differential detection operation is applied to the change rate sequence, and the point in time when the difference value in the change rate sequence exceeds the transition detection threshold is marked as the occurrence time of the morphological transition event. In this embodiment, the transition detection threshold is statistically obtained based on a large number of historical cycle test samples of lithium-sulfur battery cathode materials of the same system. First, local morphological change rate sequences of sulfur fixation evolution trajectories from multiple sets of samples with known sulfur fixation performance of varying quality are collected. The normal fluctuation range of the change rate difference results when no sulfur fixation anomaly occurs is statistically analyzed, and the upper boundary of this normal fluctuation range is used as the basic reference value for the transition detection threshold. Then, the threshold is adapted and corrected by combining the battery system, charge / discharge rate, and electrolyte formulation of the battery under test to obtain the actual transition detection threshold used in this test. This threshold is not a fixed constant but is adaptively selected according to the test conditions of the battery under test, used to distinguish whether the sulfur fixation evolution trajectory belongs to a normal, gradual evolution or a morphological transition caused by an sulfur fixation anomaly.

[0031] Tracing back to the occurrence time, a sulfur fixation evolution trajectory segment within a preset observation window before and after the occurrence time is extracted. Simultaneously, the set of polygonal grid cells in the dynamic topology traversed by this sulfur fixation evolution trajectory segment is recorded. The sulfur fixation evolution trajectory segment and the polygonal grid cell set together constitute the sulfur fixation anomaly feature. Using the sulfur fixation anomaly feature as input, a sulfur fixation performance analyzer based on field evolution feedback is driven. This process involves performing time-frequency joint analysis on the signal segments within the sulfur fixation anomaly feature, extracting the dominant distortion component and distortion energy distribution in its time spectrum as signal distortion features. The dynamic topology region within the sulfur fixation anomaly feature is analyzed, and the rate of change of geometric parameters and angular offset of all polygonal grid cells within this region are calculated as topology configuration distribution features. The signal distortion features and topology configuration distribution features are input into a pre-trained evolutionary decision network. The evolutionary decision network outputs instructions to apply expansion, contraction, or rotational deformation to the target region of the dynamic topology, along with the deformation amplitude and direction corresponding to each deformation instruction, collectively constituting the field calibration evolution instructions.

[0032] In practice, the local morphological change rate is calculated along each sulfur fixation evolution trajectory with a fixed step size, forming a change rate sequence for the sulfur fixation evolution trajectory. The fixed step size corresponds to the fixed Euclidean distance the sulfur fixation evolution trajectory moves in the two-dimensional sulfur fixation performance evolution field. The local morphological change rate is obtained by calculating the angular change rate of the vector formed by the current point, the previous point, and the next point on the sulfur fixation evolution trajectory. A sliding difference detection operation is applied to the change rate sequence. The sliding difference detection operation uses a sliding window of fixed width and calculates the first difference between adjacent change rate values ​​within the window. The formula for calculating the difference value is expressed as:

[0033] Where: symbol Indicates in sequence index The difference at point, sign The sequence of changes in the sulfur fixation evolution trajectory is represented in the index. The local morphological change rate value at a given location is used to detect the point in the change rate sequence where the difference value exceeds the transition detection threshold. This point is marked as the occurrence time of the morphological transition event. The transition detection threshold is a preset constant. Backtracking to the occurrence time, segments of the sulfur fixation evolution trajectory within a preset observation window before and after the occurrence time are extracted. Simultaneously, the set of polygonal grid cells in the dynamic topology traversed by the sulfur fixation evolution trajectory segments is recorded. The sulfur fixation evolution trajectory segments and the set of polygonal grid cells together constitute the sulfur fixation anomaly feature. The transition detection threshold used here for difference value comparison is the same parameter calibrated as the transition detection threshold used in the previous section for judging the local morphological change rate of the sulfur fixation evolution trajectory, and will not be calibrated again. When the difference value calculated by the difference is greater than this transition detection threshold, it is determined that a morphological transition has occurred at that location.

[0034] In some embodiments, the capture of morphological transition events is compared with the behavioral differences of the sulfur fixation evolution trajectory in the early and late stages of cycling. In the early stages of cycling, the rate of change sequence of the sulfur fixation evolution trajectory is usually flat, and the frequency of the difference value exceeding the transition detection threshold is low. In the late stages of cycling, due to the intensification of polysulfide shuttle, the sulfur fixation evolution trajectory may fluctuate drastically, resulting in a significant increase in the frequency of the difference value exceeding the transition detection threshold in the rate of change sequence. The frequency difference is a comparative indicator for identifying the stage of battery performance degradation. Using sulfur fixation anomaly features as input, a sulfur fixation performance analyzer based on field evolution feedback is driven. The process involves performing time-frequency joint analysis on the signal segments within the sulfur fixation anomaly features, extracting the dominant distortion components and distortion energy distribution in the time spectrum as signal distortion features. The time-frequency joint analysis uses short-time Fourier transform. The dominant distortion components are the set of frequency components in the time spectrum whose energy exceeds a certain proportion of the average energy, and the distortion energy distribution is the energy density distribution of these dominant distortion components in the time and frequency dimensions.

[0035] The dynamic topological region within the sulfur fixation anomaly is analyzed, and the rate of change of geometric parameters and angular offset of all polygonal grid cells within this region are calculated as topological configuration distribution features. The rate of change of geometric parameters refers to the rate of change of the area of ​​the polygonal grid cells at adjacent sampling times, and the angular offset refers to the deviation of the interior angles of the polygonal grid cells from the average interior angles of their standard regular polygons. Signal distortion features and topological configuration distribution features together constitute a quantitative description of the sulfur fixation anomaly state. These features are input into a pre-trained evolutionary decision network, a deep neural network with multiple hidden layers. The network outputs instructions to apply expansion, contraction, or rotational deformation to the target region of the dynamic topological region, along with the deformation amplitude and direction corresponding to each deformation instruction, collectively constituting the field calibration evolution instructions. Optionally, the logic for generating deformation commands can also be explained based on data comparison. When signal distortion characteristics show that high-frequency distortion energy dominates and topological configuration distribution characteristics show that angular offsets are generally large, the evolutionary decision network tends to output commands to apply rotational deformation to the target region, aiming to disrupt the disordered topological structure. When signal distortion characteristics show that low-frequency distortion energy is concentrated and topological configuration distribution characteristics show that the rate of change of geometric parameters exhibits a unidirectional contraction trend, the evolutionary decision network tends to output commands to apply expansion deformation. The condition of generally large angular offsets has an objective criterion: statistically analyze all polygonal mesh elements within the target topological region, first calculate the absolute value of the angular offset for each mesh element, and then calculate the arithmetic mean of the absolute values ​​of the angular offsets of the mesh elements in that region. Simultaneously, obtain the arithmetic mean of the absolute values ​​of the angular offsets of the topological regions of all historical normal sulfur fixation samples. When satisfied If so, it is determined that the angular offset of the topological region is generally large.

[0036]

[0037] In the formula: The arithmetic mean of the absolute values ​​of the angular offsets of the polygonal grid cells in the target region; This represents the total number of polygonal grid cells within the target area. For the first The angular offset of each polygonal grid cell; The preset comparison coefficients were obtained by comparing and calibrating a large amount of topological data of normal and abnormal samples. The absolute value of the angular offset of historical normal sulfur fixation samples is the arithmetic mean baseline value.

[0038] In some embodiments, the training data for the pre-trained evolutionary decision network comes from a large number of historical battery cycling tests, which identify sulfur fixation anomalies and their corresponding valid field calibration operations. The evolutionary decision network establishes a mapping relationship from features to instructions through supervised learning. In a specific implementation, the field calibration evolution instructions are output in vector form. The vector contains the identifier of the target region, the type encoding of the deformation operation, and the deformation amplitude components along the horizontal and vertical axes of the two-dimensional sulfur fixation performance evolution field. This provides explicit and executable parameters for subsequently applying calibration deformation to the dynamic characterization topology.

[0039] In one embodiment of the present invention, according to the field calibration evolution command, a corresponding calibration deformation is applied to the dynamic characterization topology in the sulfur fixation performance evolution field. This process involves locating the target region specified by the field calibration evolution command in the two-dimensional sulfur fixation performance evolution field. The target region is identified by a set of polygonal mesh cells. The vertex coordinates of all polygonal mesh cells within the target region are collaboratively updated according to the deformation type and magnitude in the field calibration evolution command. After the vertex coordinates are updated, the connection relationships and geometric properties of all affected polygonal mesh cells are recalculated and updated, completing the construction of the dynamic characterization topology after calibration deformation. Based on the new sulfur fixation evolution trace distribution, quantitative results of sulfur fixation performance for lithium-sulfur battery cathode materials are generated. This process involves identifying stable sulfur fixation channels in the new sulfur fixation evolution trace distribution. Stable sulfur fixation channels are defined by the morphological change rate of the sulfur fixation evolution trace continuously being lower than a stable threshold. The stable sulfur fixation channels are mapped back to the electrochemical signal space and converted into steady-state voltage reference commands and sulfur fixation state commands. Multisulfide shuttle noise is stripped from the electrochemical signal to separate the main sulfur fixation mode and the residual shuttle oscillation mode. The steady-state sulfur fixation signal, defined by the steady-state voltage reference command and the sulfur fixation state command, is fused with the residual shuttle oscillation mode to synthesize a comprehensive sulfur fixation performance indicator signal. Based on this comprehensive sulfur fixation performance indicator signal, quantitative results of the sulfur fixation performance for lithium-sulfur battery cathode materials are generated.

[0040] In practical implementation, the target region specified by the field calibration evolution command is located in the two-dimensional sulfur fixation performance evolution field. The target region is identified by a set of polygonal mesh elements. The field calibration evolution command contains a list of identification numbers for each polygonal mesh element in the target region. According to the deformation type and deformation amplitude in the field calibration evolution command, the vertex coordinates of all polygonal mesh elements in the target region are updated collaboratively. For expansion deformation, the deformation amplitude includes the lateral expansion coefficient and the longitudinal expansion coefficient. The vertex coordinate update formula is expressed as:

[0041] Where: symbol Indicates the updated vertex New coordinates, symbol Represents vertices The original coordinates, symbol Represents the geometric center coordinates of the target region, symbol Represents the lateral expansion coefficient, symbol This represents the longitudinal expansion coefficient, the value of which is given by the field calibration evolution command. For contraction deformation, the coefficient is negative; for rotation deformation, the vertex coordinates are rotated based on a given rotation angle. After the vertex coordinates are updated, the connectivity and geometric properties of all affected polygonal mesh elements are recalculated and updated. The connectivity is redefined using the Delaunay triangulation rule based on the updated vertex coordinates. The geometric properties include the area and interior angles of the polygonal mesh elements. This completes the construction of the dynamic characterization topology after calibration deformation. The calibration deformation aims to optimize the structure of the two-dimensional sulfur fixation performance evolution field to adapt to the actual evolution mode of sulfur fixation performance.

[0042] In some embodiments, quantitative results of sulfur fixation performance for lithium-sulfur battery cathode materials are generated based on a new sulfur fixation evolution trace distribution. The process involves identifying stable sulfur fixation channels in the new sulfur fixation evolution trace distribution. Stable sulfur fixation channels are defined by the morphological change rate of the sulfur fixation evolution trace being consistently lower than a stability threshold. On the dynamically characterized topology after calibration, sulfur fixation evolution traces are regenerated using the method described in the embodiments. The morphological change rate of the newly generated sulfur fixation evolution traces is observed within a preset observation period. The preset observation period covers a complete charge-discharge cycle. If the maximum morphological change rate of a certain segment of the sulfur fixation evolution trace is consistently lower than the stability threshold throughout the entire observation period, then that segment of the sulfur fixation evolution trace is determined to be a stable sulfur fixation channel. The data comparison reveals changes in the number and length of stable sulfur fixation channels before and after calibration deformation. Before calibration deformation, due to the failure of the dynamic characterization topology to accurately reflect the field structure, the identified stable sulfur fixation channels may be few in number or discontinuous. After calibration deformation optimizes the field structure, the regenerated sulfur fixation evolution traces are more rationally distributed, and the number of identified stable sulfur fixation channels may increase, while the paths are more continuous and complete. This before-and-after comparison verifies the effectiveness of calibration deformation. The stable sulfur fixation channels are mapped back to the electrochemical signal space and converted into steady-state voltage reference commands and sulfur fixation state commands. Simultaneously, multisulfide shuttle noise is stripped from the original voltage and current signal sequences to separate the main sulfur fixation mode and the residual shuttle oscillation mode.

[0043] In practical implementation, adaptive noise-complete empirical mode decomposition is applied to the voltage and current signal sequences to obtain a series of intrinsic mode components arranged from high frequency to low frequency. Based on the instantaneous frequency of the intrinsic mode components, the intrinsic mode components whose instantaneous frequency is consistent with the main frequency of the electrochemical reaction are selected. These components are superimposed to reconstruct the main sulfur fixation mode. The original electrochemical signal is subtracted from the main sulfur fixation mode, and the remaining waveform component is the residual shuttle oscillation mode characterizing the polysulfide shuttle side reaction. Optionally, the steady-state sulfur fixation signal defined by the steady-state voltage reference command and the sulfur fixation state command is fused with the residual shuttle oscillation mode to synthesize a comprehensive sulfur fixation performance indication signal. The process involves generating a standard electrochemical reference waveform as the steady-state sulfur fixation signal based on the steady-state voltage reference command and the sulfur fixation state command. The standard electrochemical reference waveform is an idealized waveform with a constant voltage plateau and a smooth charge-discharge slope. The steady-state sulfur fixation signal and the residual shuttle oscillation mode are superimposed in the time domain to obtain a preliminary performance indication signal. In some embodiments, the preliminary performance indication signal is normalized and smoothed to ensure that its value is within a preset quantization range between zero and one and that the waveform is continuous. The normalization adopts the minimum-maximum scaling method, and the smoothing adopts the moving average filter. The processed signal is the comprehensive sulfur fixation performance indication signal used to quantify the sulfur fixation performance. Based on the comprehensive sulfur fixation performance indication signal, the quantification result of the sulfur fixation performance of the lithium-sulfur battery cathode material is generated. The quantification result can be expressed as the integral area value of the comprehensive sulfur fixation performance indication signal in a complete cycle. The size of the area value directly corresponds to the quality of the sulfur fixation performance of the cathode material.

[0044] In one embodiment of the present invention, stable sulfur fixation channels are identified in the new sulfur fixation evolution trajectory distribution. This process involves regenerating the sulfur fixation evolution trajectory on the dynamically characterized topology after calibration and deformation. The morphological change rate of the newly generated sulfur fixation evolution trajectory is observed within a preset observation period. If the maximum morphological change rate of a certain segment of the sulfur fixation evolution trajectory remains below a stability threshold throughout the entire observation period, that segment is determined to be a stable sulfur fixation channel. The starting coordinates, ending coordinates, and the sequence of grid cells traversed by all stable sulfur fixation channels in the two-dimensional sulfur fixation performance evolution field are recorded. The stable sulfur fixation channels are mapped back to the electrochemical signal space and converted into steady-state voltage reference commands and sulfur fixation state commands. This process involves calculating the average sulfur embedding capacity and average voltage hysteresis value of each stable sulfur fixation channel in the two-dimensional sulfur fixation performance evolution field based on its starting and ending coordinates. Through a preset electrochemical mapping relationship, the average sulfur embedding capacity and average voltage hysteresis value are converted into steady-state voltage reference commands and sulfur fixation state commands characterizing sulfur fixation capability under the corresponding cyclic state.

[0045] In practice, the sulfur fixation evolution traces are redrawn using the trace generation method on the dynamically characterized topology after calibration and deformation. The morphological change rate of the newly generated sulfur fixation evolution traces is observed within a preset observation period, which covers at least one complete charge-discharge cycle. The morphological change rate is calculated at a fixed sampling interval. If the maximum morphological change rate of a certain segment of the sulfur fixation evolution trace remains below the stability threshold throughout the entire observation period, then that segment of the sulfur fixation evolution trace is determined to be a stable sulfur fixation channel. The starting coordinates, ending coordinates, and grid cell sequence traversed by all stable sulfur fixation channels in the two-dimensional sulfur fixation performance evolution field are recorded. The starting and ending coordinates record the abscissa and ordinate values ​​of the starting and ending positions of the stable sulfur fixation channel in the two-dimensional sulfur fixation performance evolution field, respectively. The grid cell sequence traversed records the identifier of each polygonal grid cell passed through by the stable sulfur fixation channel. The data comparison reflects the difference in the properties of the stable sulfur fixation channels identified before and after calibration deformation. Before calibration deformation, due to field distortion, the identified channels may be short, discontinuous and few in number. After calibration deformation, the field structure is optimized, and the identified stable sulfur fixation channels usually have longer continuous paths and more in number. See Table 1, which shows the comparison of the coordinates and lengths of the two main stable sulfur fixation channels identified before and after a typical calibration.

[0046] Table 1: Comparison of Properties of Stable Sulfur Fixation Channels Before and After Calibration Deformation

[0047] For each stable sulfur fixation channel, based on the starting and ending coordinates of the channel, the average sulfur embedding capacity and average voltage hysteresis value of the stable sulfur fixation channel in the two-dimensional sulfur fixation performance evolution field are calculated. The average sulfur embedding capacity value is calculated as the arithmetic mean of the starting and ending abscissa values, and the average voltage hysteresis value is calculated as the arithmetic mean of the starting and ending ordinate values. The calculation formulas are expressed as follows:

[0048] Where: symbol The average sulfur intercalation capacity is represented by the symbol. Represents the average voltage lag value, symbol With symbols The x-coordinate and y-coordinate values ​​of the starting point coordinates of the stable sulfur fixation channel are respectively represented by the symbols. With symbols The x-coordinate and y-coordinate values ​​represent the coordinates of the endpoint of the stable sulfur fixation channel, respectively.

[0049] In some embodiments, the average sulfur intercalation capacity and average voltage hysteresis value are converted into a steady-state voltage reference command and a sulfur fixation state command characterizing sulfur fixation capability under corresponding cycling conditions through a preset electrochemical mapping relationship. The preset electrochemical mapping relationship is a lookup table or function model obtained by fitting a large amount of experimental data. The lookup table uses the average sulfur intercalation capacity and average voltage hysteresis value as input indices, and outputs a pair of corresponding voltage reference values ​​and sulfur fixation capability score values. The voltage reference value is the steady-state voltage reference command, and the sulfur fixation capability score value is the sulfur fixation state command. Data comparison is also reflected in the differences in the converted commands. For example, in Table 1, the calibrated channel A has a lower average voltage hysteresis value and a higher average sulfur intercalation capacity value. After conversion through the electrochemical mapping relationship, a lower steady-state voltage reference command and a higher sulfur fixation state command are usually obtained, indicating that the material has better sulfur fixation performance and a more stable voltage plateau in the state corresponding to this channel.

[0050] In practical implementation, the construction of the electrochemical mapping relationship relies on benchmark testing of cathode materials with known performance, recording the average sulfur intercalation capacity, average voltage hysteresis value, and the actual steady-state voltage and sulfur fixation efficiency corresponding to their stable sulfur fixation channels, thereby establishing a reliable correspondence from field parameters to performance commands. Optionally, for a stable sulfur fixation channel, if the grid cell sequence it traverses contains a large number of cells and the average sulfur intercalation capacity value changes gradually, the mapped sulfur fixation state command value is higher, indicating that the sulfur fixation process exhibits good stability within the capacity range covered by the channel. In some embodiments, each identified stable sulfur fixation channel independently generates a set of steady-state voltage benchmark commands and sulfur fixation state commands, and the system can output multiple sets of commands to describe the performance of the material in different sulfur fixation state ranges.

[0051] See Figure 4 This is a graph showing the relationship between the sulfur fixation state command and the steady-state voltage reference command in lithium-sulfur batteries before and after sulfur fixation performance calibration. Before calibration, the sulfur fixation state command scores were 32 and 78, corresponding to steady-state voltage reference commands of 3.12V and 2.47V. After calibration, the sulfur fixation state command scores were 45 and 86, corresponding to steady-state voltage reference commands of 2.95V and 2.31V. The increase in the sulfur fixation state command score indicates enhanced sulfur fixation capability of the material; the decrease in the steady-state voltage reference command indicates a more stable voltage plateau and effective suppression of the multisulfide shuttle effect. Both curves show a negative linear correlation, verifying the electrochemical logic that "the stronger the sulfur fixation capability, the more stable the steady-state voltage." Calibration not only increased the highest sulfur fixation state command but also further reduced the steady-state voltage reference command, demonstrating the effectiveness of dynamic characterization topology calibration. By optimizing the dynamic characterization topology, the stable sulfur fixation channel becomes more continuous and longer, ultimately translating into a higher sulfur fixation state command and a more stable steady-state voltage reference command.

[0052] In one embodiment of the present invention, polysulfide shuttle noise is stripped from the electrochemical signal to separate the main sulfur fixation mode and the residual shuttle oscillation mode. This process involves applying adaptive noise-complete empirical mode decomposition (EMD) to the voltage and current signal sequences to obtain a series of intrinsic mode components. Based on the instantaneous frequencies of these intrinsic mode components, those with instantaneous frequencies consistent with the dominant frequency of the electrochemical reaction are selected, and these components are reconstructed as the main sulfur fixation mode. Subtracting the main sulfur fixation mode from the original electrochemical signal yields the residual shuttle oscillation mode. The steady-state sulfur fixation signal, defined by the steady-state voltage reference command and the sulfur fixation state command, is fused with the residual shuttle oscillation mode to synthesize a comprehensive sulfur fixation performance indicator signal. This process involves generating a standard electrochemical reference waveform as the steady-state sulfur fixation signal based on the steady-state voltage reference command and the sulfur fixation state command. Finally, the steady-state sulfur fixation signal and the residual shuttle oscillation mode are superimposed in the time domain to obtain a preliminary performance indicator signal. The preliminary performance indication signal is normalized and smoothed to ensure that its value is within the preset quantization range and the waveform is continuous. The processed signal is the comprehensive sulfur fixation performance indication signal used to quantify sulfur fixation performance.

[0053] In practice, adaptive noise-complete empirical mode decomposition (EMD) is applied to the voltage and current signal sequences. The EMD algorithm adds paired white noise copies to the original signal sequences. By performing EMD on all noisy signal sequences and averaging the results, a series of intrinsic mode components (IMCs) are obtained, arranged in descending order of frequency. Based on the instantaneous frequencies of the IMCs, IMCs whose instantaneous frequencies match the dominant frequency of the electrochemical reaction are selected. The dominant frequency of the electrochemical reaction is obtained through principal component analysis of the differential capacity spectra of a large number of standard lithium-sulfur battery constant current charge-discharge curves; it is a known characteristic frequency value. These IMCs with instantaneous frequencies matching the dominant frequency of the electrochemical reaction are superimposed and reconstructed to obtain the main sulfur fixation mode. Subtracting the main sulfur fixation mode from the original electrochemical signal leaves the residual shuttle oscillation mode, which characterizes the voltage and current fluctuations caused by side reactions such as polysulfide dissolution, diffusion, and redeposition. The data comparison is reflected in the decomposition of the same electrochemical signal at the beginning and end of the cycle. The main sulfur fixation mode obtained at the beginning of the cycle has a high energy ratio and regular waveform, while the residual shuttle oscillation mode has a small amplitude. The main sulfur fixation mode obtained at the end of the cycle may be distorted, while the amplitude and complexity of the residual shuttle oscillation mode increase significantly. This comparison intuitively reflects the intensification of polysulfide shuttle with the cycle.

[0054] In some embodiments, a standard electrochemical reference waveform is generated as a steady-state sulfur fixation signal based on a steady-state voltage reference command and a sulfur fixation state command. The steady-state voltage reference command defines the voltage plateau value, and the sulfur fixation state command defines the slope of the charge-discharge curve through a scaling factor. The generated standard electrochemical reference waveform is a piecewise linear waveform, where the plateau voltage is determined by the steady-state voltage reference command, and the slope of the ramp segment is determined by the sulfur fixation state command. The steady-state sulfur fixation signal is superimposed with the residual shuttle oscillation mode in the time domain to obtain a preliminary performance indication signal. The waveform superposition is a direct algebraic addition, and its calculation formula is expressed as follows:

[0055] Where: symbol Indicates a point in time Preliminary performance indication signal value, symbol Indicates a point in time The steady-state sulfur fixation signal value, symbol Indicates a point in time The residual shuttle oscillation mode value. The preliminary performance indication signal is normalized and smoothed to ensure that its value is within the preset quantization range and the waveform is continuous. The normalization process linearly scales the amplitude of the preliminary performance indication signal to the range of zero to one. The smoothing process uses a low-pass filter to filter the normalized signal to remove high-frequency glitches. The processed signal is the comprehensive sulfur fixation performance indication signal used to quantify sulfur fixation performance.

[0056] In practical implementation, data comparison is further accomplished by comparing the comprehensive sulfur fixation performance indicator signals obtained from different cathode materials or the same material after different cycle numbers. Materials with superior performance exhibit a flatter and slower decay of their comprehensive sulfur fixation performance indicator signal during the plateau period, while materials with deteriorating performance show a significant dip or oscillation during the plateau period. Optionally, the cutoff frequency of the low-pass filter is set to one-tenth of the dominant frequency of the electrochemical reaction to ensure effective smoothing while preserving the main reaction information. In some embodiments, the preset quantization range is set to zero to one, where one represents ideal sulfur fixation performance and zero represents failed sulfur fixation performance. The average or integral value of the comprehensive sulfur fixation performance indicator signal over the entire charge-discharge cycle can be used as the final quantification result of sulfur fixation performance. Ultimately, the comprehensive sulfur fixation performance indicator signal fully integrates information on steady-state sulfur fixation capability and multisulfide shuttle oscillation, providing a comprehensive and quantifiable performance index.

[0057] See Figure 5This is a voltage comparison chart of a lithium-sulfur battery before and after cycling, showing the voltage-capacity curves at the beginning and end of cycling, intuitively reflecting the performance degradation during battery cycling. In the initial stage of cycling, the voltage generally exhibits a typical discharge curve pattern of first rising and then falling, peaking at approximately 25% capacity, reaching 3.48V. The curve is smooth with no significant fluctuations, indicating good sulfur fixation performance, weak polysulfide ion shuttle effect, and a stable voltage plateau at this stage. Throughout the full capacity range (0~100%), the voltage remains between 1.4 and 3.5V, with the final voltage at approximately 1.45V, maintaining full capacity. At the end of cycling, the overall voltage level is significantly lower than in the initial stage, accompanied by severe high-frequency fluctuations. The peak voltage is only about 3.1V, and the voltage drops rapidly after exceeding 60% capacity, reaching a minimum of 0.95V at the end. These voltage fluctuations directly reflect the intensified polysulfide shuttle effect and deteriorated sulfur fixation performance, leading to a significant decrease in voltage stability.

[0058] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for detecting the sulfur fixation performance of lithium-sulfur battery cathode materials, characterized in that, include: The electrochemical signals of the cathode material of a lithium-sulfur battery at multiple sampling times during a preset charge-discharge cycle test are obtained. The electrochemical signals include voltage signal sequences and current signal sequences. The electrochemical signal is injected into the sulfur fixation performance evolution field for dynamic analysis. A dynamic characterization topology that deforms with the battery cycle state is constructed in the sulfur fixation performance evolution field. Sulfur fixation evolution traces are generated between the nodes of the dynamic characterization topology based on the voltage signal sequence and the current signal sequence. The morphological transition events of the sulfur fixation evolution trajectory are monitored and captured. When the local morphological change rate of the sulfur fixation evolution trajectory exceeds the transition detection threshold, the signal segment of the sulfur fixation evolution trajectory and its corresponding dynamic characterization topological region are extracted to form sulfur fixation anomaly features. Using the sulfur fixation anomaly features as input, a sulfur fixation performance analyzer based on field evolution feedback is driven. The sulfur fixation performance analyzer based on field evolution feedback outputs field calibration evolution instructions based on the distortion features of signal segments within the sulfur fixation anomaly features and the configuration distribution of the dynamic characterization topology region. According to the field calibration evolution command, a corresponding calibration deformation is applied to the dynamic characterization topology in the sulfur fixation performance evolution field, and the dynamic characterization topology after calibration deformation generates a new sulfur fixation evolution trace distribution. Based on the new sulfur fixation evolution trajectory distribution, quantitative results of sulfur fixation performance for lithium-sulfur battery cathode materials are generated.

2. The method for detecting the sulfur fixation performance of lithium-sulfur battery cathode materials according to claim 1, characterized in that, The step of injecting the electrochemical signal into the sulfur fixation performance evolution field for dynamic analysis, and constructing a dynamic characterization topology in the sulfur fixation performance evolution field that deforms with changes in battery cycling state, includes: The instantaneous values ​​of sulfur embedding capacity and voltage hysteresis are calculated at each sampling time based on the voltage signal sequence and the current signal sequence. A two-dimensional sulfur fixation performance evolution field is constructed with the instantaneous value of sulfur embedding capacity as the horizontal axis and the instantaneous value of voltage hysteresis as the vertical axis, and the sulfur fixation state point at each sampling time is plotted in the two-dimensional sulfur fixation performance evolution field. Connect the sulfur fixation state points at adjacent sampling times in the two-dimensional sulfur fixation performance evolution field to form a sulfur fixation evolution trajectory line; Based on the spatial distribution density of the sulfur fixation evolution trajectory, a non-uniform polygonal mesh is automatically generated in the two-dimensional sulfur fixation performance evolution field to cover the sulfur fixation evolution trajectory. The vertex density of the polygonal mesh is positively correlated with the local morphological change rate of the sulfur fixation evolution trajectory. The polygonal mesh is a dynamic topology that adjusts its vertex positions and connection relationships as the sulfur fixation state points change.

3. The method for detecting the sulfur fixation performance of lithium-sulfur battery cathode materials according to claim 2, characterized in that, The process of generating sulfur fixation evolution traces between nodes in the dynamically characterized topology based on voltage and current signal sequences includes: For each polygonal mesh cell representing the dynamic topology, calculate the evolution gradient vector of the instantaneous values ​​of the sulfur embedding capacity and voltage hysteresis corresponding to its vertices; The evolution gradient vectors of multiple vertices within each polygonal grid cell are weighted and fused to obtain the sulfur fixation evolution direction vector of that polygonal grid cell. Along the sulfur fixation evolution direction vector field, a trace is drawn on the dynamic characterization topology from the high sulfur intercalation capacity region to the low sulfur intercalation capacity region. The trace is the sulfur fixation evolution trace that characterizes the real-time evolution path and intensity of sulfur fixation performance.

4. The method for detecting the sulfur fixation performance of lithium-sulfur battery cathode materials according to claim 3, characterized in that, The monitoring and capture of morphological transition events in the sulfur fixation evolution trajectory includes: The local morphological change rate is calculated along each sulfur fixation evolution trajectory with a fixed step size to form a sequence of change rates of sulfur fixation evolution trajectories; Apply the sliding difference detection operation to the rate of change sequence to detect the moment when the difference value in the rate of change sequence exceeds the transition detection threshold, and mark it as the moment when the morphological transition event occurs; Back to the time of occurrence, extract the sulfur fixation evolution trajectory segment within the preset observation window before and after the time of occurrence, and record the set of polygonal grid cells in the dynamic characterization topology through which the sulfur fixation evolution trajectory segment passes. The sulfur fixation evolution trajectory segment and the set of polygonal grid cells together constitute the sulfur fixation anomaly feature.

5. The method for detecting the sulfur fixation performance of lithium-sulfur battery cathode materials according to claim 4, characterized in that, The step of using the aforementioned sulfur fixation anomaly characteristics as input to drive a sulfur fixation performance analyzer based on field evolution feedback includes: The signal segments within the sulfur fixation anomaly feature are subjected to joint time-frequency analysis to extract the dominant distortion component and distortion energy distribution in their time spectrum as signal distortion features. The dynamic topological region within the sulfur fixation anomaly is analyzed, and the rate of change of geometric parameters and angular offset of all polygonal mesh elements within this region are calculated as topological configuration distribution characteristics. The signal distortion features and topological configuration distribution features are input into a pre-trained evolutionary decision network. The evolutionary decision network outputs instructions to apply expansion, contraction or rotation deformation to the target region that dynamically represents the topology, as well as the deformation amplitude and direction corresponding to each deformation instruction, which together constitute the field calibration evolution instructions.

6. The method for detecting the sulfur fixation performance of lithium-sulfur battery cathode materials according to claim 5, characterized in that, The step of applying corresponding calibration deformation to the dynamic characterization topology in the sulfur fixation performance evolution field according to the field calibration evolution command includes: In the two-dimensional sulfur fixation performance evolution field, the target region specified by the field calibration evolution command is located, and the target region is identified by a set of polygonal mesh cells; According to the deformation type and deformation magnitude in the field calibration evolution command, the vertex coordinates of all polygonal mesh elements in the target area are updated collaboratively. After updating the vertex coordinates, the connectivity and geometric properties of all affected polygon mesh cells are recalculated and updated to complete the construction of the dynamic representation topology after calibration deformation.

7. The method for detecting the sulfur fixation performance of lithium-sulfur battery cathode materials according to claim 6, characterized in that, The generation of quantitative results for the sulfur fixation performance of lithium-sulfur battery cathode materials based on the new sulfur fixation evolution trajectory distribution includes: Stable sulfur fixation channels were identified in the new sulfur fixation evolution trajectory distribution. These stable sulfur fixation channels were defined by the morphological change rate of the sulfur fixation evolution trajectory being consistently below a stability threshold. The stable sulfur fixation channel is mapped back to the electrochemical signal space and converted into steady-state voltage reference command and sulfur fixation state command. Simultaneously, polysulfide shuttle noise stripping is performed on the electrochemical signal to separate the main sulfur fixation mode and the residual shuttle oscillation mode; The steady-state sulfur fixation signal defined by the steady-state voltage reference command and the sulfur fixation state command is fused with the residual shuttle oscillation mode to synthesize a comprehensive sulfur fixation performance indicator signal. Based on the comprehensive sulfur fixation performance indicator signal, quantitative results of sulfur fixation performance for lithium-sulfur battery cathode materials are generated.

8. The method for detecting the sulfur fixation performance of lithium-sulfur battery cathode materials according to claim 7, characterized in that, The identification of stable sulfur fixation channels in the new sulfur fixation evolution trajectory distribution includes: The sulfur solidification evolution trace is regenerated on the dynamically characterized topology after calibration deformation; The morphological change rate of newly generated sulfur fixation evolution traces is observed within a preset observation period. If the maximum morphological change rate of a certain sulfur fixation evolution trace is consistently lower than the stability threshold throughout the entire observation period, then the sulfur fixation evolution trace is determined to be a stable sulfur fixation channel. Record the starting coordinates, ending coordinates, and grid cell sequence of all stable sulfur fixation channels in the two-dimensional sulfur fixation performance evolution field.

9. The method for detecting the sulfur fixation performance of lithium-sulfur battery cathode materials according to claim 8, characterized in that, The process of mapping the stable sulfur fixation channel back to the electrochemical signal space and converting it into a steady-state voltage reference command and a sulfur fixation state command includes: For each stable sulfur fixation channel, the average sulfur intercalation capacity and average voltage hysteresis value of the stable sulfur fixation channel in the two-dimensional sulfur fixation performance evolution field are calculated based on its starting point coordinates and ending point coordinates. By using a pre-defined electrochemical mapping relationship, the average sulfur intercalation capacity value and the average voltage hysteresis value are converted into the steady-state voltage reference command and the sulfur fixation state command characterizing the sulfur fixation capability under the corresponding cycle conditions.

10. A method for detecting the sulfur fixation performance of lithium-sulfur battery cathode materials according to claim 9, characterized in that, The process of stripping polysulfide shuttle noise from the electrochemical signal to separate the main sulfur-fixing mode and the residual shuttle oscillation mode includes: Adaptive noise-complete empirical mode decomposition is applied to voltage signal sequences and current signal sequences to obtain a series of intrinsic mode components. Based on the instantaneous frequency of the intrinsic mode components, intrinsic mode components whose instantaneous frequency is consistent with the main frequency of the electrochemical reaction are selected, and these components are reconstructed into the main sulfur fixation mode. Subtracting the main sulfur fixation mode from the original electrochemical signal, the remaining waveform components are the residual shuttle oscillation modes; The process of fusing the steady-state sulfur fixation signal defined by the steady-state voltage reference command and the sulfur fixation state command with the residual shuttle oscillation mode to synthesize a comprehensive sulfur fixation performance indicator signal includes: Based on the steady-state voltage reference command and the sulfur fixation state command, a standard electrochemical reference waveform is generated as the steady-state sulfur fixation signal; The steady-state sulfur fixation signal and the residual shuttle oscillation mode are superimposed in the time domain to obtain a preliminary performance indication signal; The preliminary performance indication signal is normalized and smoothed to ensure that its value is within the preset quantization range and the waveform is continuous. The processed signal is the comprehensive sulfur fixation performance indication signal used to quantify sulfur fixation performance.

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