Shengyu
Tao‡
af,
Mengtian
Zhang‡
a,
Zixi
Zhao‡
a,
Haoyang
Li
b,
Ruifei
Ma
a,
Yunhong
Che
c,
Xin
Sun
d,
Lin
Su
a,
Chongbo
Sun
a,
Xiangyu
Chen
a,
Heng
Chang
a,
Shiji
Zhou
a,
Zepeng
Li
a,
Hanyang
Lin
a,
Yaojun
Liu
e,
Wenjun
Yu
e,
Zhongling
Xu
e,
Han
Hao
b,
Scott
Moura
f,
Xuan
Zhang
*a,
Yang
Li
*a,
Xiaosong
Hu
*g and
Guangmin
Zhou
*a
aTsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, China. E-mail: xuanzhang@sz.tsinghua.edu.cn; yangli@sz.tsinghua.edu.cn; guangminzhou@sz.tsinghua.edu.cn
bState Key Laboratory of Intelligent Green Vehicle and Mobility, Tsinghua University, Beijing, China
cDepartment of Energy, Aalborg University, Aalborg, Denmark
dIntegrated Research on Energy, Environment and Society (IREES), Energy and Sustainability Research Institute Groningen (ESRIG), University of Groningen, Groningen, The Netherlands
eSunwoda Mobility Energy Technology Co., Ltd., Shenzhen, China
fEnergy, Controls, and Applications Lab (eCAL), Department of Civil and Environmental Engineering, University of California, Berkeley, California, USA
gCollege of Mechanical and Vehicle Engineering, Chongqing University, Chongqing, China. E-mail: xiaosonghu@ieee.org
First published on 14th January 2025
Manufacturing complexities and uncertainties have impeded the transition from material prototypes to commercial batteries, making their verification a critical quality assessment link. A fundamental challenge is to decouple electrochemical interactions for establishing a quantitative mapping from electrochemical parameters to macro battery performance. Here, we show that the proposed physics-informed learning model can quantify and visualize temporally resolved thermodynamic and kinetic parameters from field accessible electric signals, facilitating a non-destructive degradation pattern decoupling. The lifetime trajectory prediction is 25 times faster than the traditional capacity calibration test while retaining a 95.1% average accuracy across temperatures, underpinned by projected electrochemical data from early cycle observations which have not yet been established. We rationalize this predictability to the interpretation of statistical insights from material-agnostic featurization, excited by a multistep charging scheme with different current intensities and their switching conditions. The waste management of defective prototypes is enabled by statistically and non-destructively interpreting internal electrochemical states, demonstrating a 19.76 billion USD defective material recycling market by 2060. This paper highlights the potential of revisiting electrochemical degradation behaviors using physics-informed learning and dynamic current excitations, facilitating next-generation battery manufacturing, reuse, and recycling sustainability.
Broader contextBattery research and development (R&D) faces fierce competition in selecting future energy storage technologies but generating endless defective battery prototypes. Performance mismatches between theoretical designs and as-manufactured batteries remain a bottleneck due to time-consuming, costly, and often destructive verification. Although machine learning has been well-documented in battery R&D, it fails to decouple electrochemical degradation patterns that support interpretable decisions. Here, distinct from purely statistical modeling, we compute thermodynamic and kinetic degradation parameters from initial manufacturing differences among normally identical batteries and project them into future states which have not yet been established, saving data acquisition costs otherwise required for model inference. This physics-informed model shows promise in merging electrochemical priors into statistical learning, demonstrating sustainable and economic superiorities by managing defective prototype batteries before massive production. |
In battery manufacturing, capacity calibration is a standardized way to verify the prototype quality.9 This conventional method needs extensive durability testing time on selected samples to statistically validate quality in batches.10,11 Although accelerated tests are conducted under harsh conditions, such as higher current densities and temperatures, they still necessitate extensive cycles per sample until end-of-life (EOL), such as 80% of the nominal capacity. However, translating outcomes from accelerated tests to standard conditions poses challenges for novel battery research and development (R&D) due to the uneven quality benchmarking conditions.4 The challenges are amplified by initial manufacturing variabilities (IMVs), resulting from material preparation, assembly, and coupled degradation patterns, such as voltage fade and electrochemical dynamics.12–16 The degradation patterns, including kinetics and thermodynamics, manifest as impedance increase, loss of lithium-ion inventory (LLI), and loss of active material (LAM), and are traditionally analyzed by destructive post-mortem methods, contradicting practical needs of timely quality feedback. Efforts to mitigate these degradations prioritize automated production lines in reducing human error and improving stringent control of micro properties.17–19 Unfortunately, the destructive characterizations and control of micro parameters are still unaffordable in massive battery production practices.
Emerging technologies such as smart manufacturing and digital twins enable monitoring of battery production, yet integrating recent advances like novel sensors for internal detection faces challenges in production line integration and long-term use.20–27 Manufacturers find the available signals, such as current, voltage, and capacity, integrated with machine learning, promising for predicting battery lifetime trajectories and internal states under diverse conditions.28–35 However, these models struggle to predict intermediate degradations, with lifetime trajectory prediction posing a greater challenge due to the need for more sensory data that has not yet been established at the time of prediction.36–38 Despite the extrapolation abilities, the statistical model still relies on the availability of long-term observational data, where necessary data collecting time conflicts with the goals of reducing verification time and costs.39 Though mitigating data requirements, empirical models extrapolate lifetime trajectories with significant requirements for parameter tunings under changing operation conditions. Stable and interpretable insights into degradation patterns are critical to projecting the current chemical process data into future states by using physical laws, as they can mitigate the need for extra data curation experiments. However, the coupled degradation patterns make the electrochemical modeling of underlying physics even more challenging. The integration of physical knowledge into the statistical models shows great promise in balancing experimental data acquisition and experiment-free electrochemical modeling, particularly relevant to advising rational reuse, recycling, and remanufacturing of defective products to improve their lifecycle sustainability,40,41 but remains significantly underexplored.
In this study, we introduce a lifetime trajectory prediction method using early cycle data (50 cycles, 4% of total lifetime) from both newly manufactured and accelerated aging batteries to supervise a statistical model, shown in Fig. 1a. The proposed method predicts entire battery lifetime trajectories, rather than EOL points, by computing thermodynamic and kinetic parameters and projecting them to future states that have not yet been established for model inference. Without directly measuring the internal states, we use projected chemical processes to bypass the need for post-failure observational data requirements, otherwise obtained from lengthy and costly capacity calibration tests. Fig. 1b shows IMVs through stepwise charge acceptance, helping to adjust chemical process projections considering cell-to-cell variability. The proposed statistical model forecasts chemical processes across temperatures from early data, further used as an input to the lifetime trajectory prediction model. The proposed method prioritizes studying degradations, including thermodynamic and kinetic losses and polarizations, excited from a multi-step charging profile with different current intensities and switching conditions. Fig. 1c details the method application for battery R&D, enabling timely and accurate quality assessment and waste management of defective prototypes, minimizing economic and environmental losses. This paper highlights the model interpretability, non-destructive lifetime trajectory prediction, and sustainable potential in emerging applications for next-generation prototype quality assessment and waste management before massive battery production.
Fig. 2a depicts battery capacity declines over cycles, with high temperatures reducing lifespan. Despite identical cycling and manufacturing conditions, variations in degradation trajectories are evident. Fig. 2b demonstrates the key distinction from constant current verification, using a multi-step charge profile relevant to EV fast charging. This protocol charges 75% of the total SOC within 20 minutes, across a range of 0.33C to 3C with 9 consecutive steps. Fig. 2c details SOC allocations per step, with cut-off voltages (U1 to U9) representing charge acceptance at each SOC. Fig. 2d shows these voltages against temperature, indicating a typical voltage decrease as the temperature rises, further battery-averaged in Fig. 2e. Minor voltage variations at a constant temperature signify different charge acceptance in ostensibly identical batteries. IMVs, represented by these voltage variances, are graphed in Fig. 2f as temperature functions, displaying bowl-shaped curves across all steps barring U1. The minor deviations of U1 at 25 °C are noise-sensitive with an mV level signal. IMVs decrease then increase around 45 °C, suggesting temperature-induced reaction accelerations. The bowl-shaped lifetime variations (Fig. S4 and S5, ESI†) establish an immediate correlation between IMVs and macro lifetime, with lifespans (EOL73) of 1218, 1180, 958, and 661 cycles at 25, 35, 45, and 55 °C, respectively, as displayed in Fig. 2g. These trends are consistent across temperatures, affirming that initial IMV probing deterministically affects macro capacity. At 55 °C, unstable correlations (Fig. S5, ESI†) might stem from side reactions surpassing normal reaction rates during extended cycling, a diminishing relationship illustrated in Fig. S6 (ESI†). Thus, challenges persist with long-term degradation characterization due to temporal- and thermal varying conditions. The batch quality is affirmed by the Arrhenius plot depicted in Fig. 2h, where a consistent line across 25 to 55 °C indicates no significant degradation mechanism alteration under fast charging, thus the verification inflicts no damages to battery prototypes.42 Leveraging Arrhenius principles allows early verification by comparing AT (Arrhenius transferability) metric between baseline (accelerated aging data) and novel battery early cycle data, as shown in Fig. 2i.
Fig. 3d illustrates extracted features of the chemical process over the first 800 cycles, with the ohmic resistance revealing an increase in ohmic resistance, i.e., a decline in kinetic capacity, across most switching stages, indicative of kinetic deviations in identical batteries and the magnification of IMVs during cycling (Fig. S11–S14, ESI†). Similarly, the lumped resistance, integrating aspects of ohmic, electrochemical, and concentration resistance, shows reduced dynamic capacity and larger deviations over time (Fig. S15–S18, ESI†). Charge acceptance decreases, as evidenced by growing voltage gradient (i.e., polarization rate) for a given stepwise cut-off voltage, suggesting that even slight initial IMVs have a compounding impact on long-term performance, as further indicated by trends in Fig. S19–S22 (ESI†).
Given the impact of IMVs on chemical process variations, battery prototype verification must account for these influences to ensure accuracy. We utilize early-cycle IMVs as benchmarks for tracking chemical process evolution. Our machine learning model, informed by physics, uses these predicted chemical processes as proxies for the actual internal states, operating on the premise that the battery lifetime trajectory can be deduced from these internal insights. Our approach involves a three-stage machine learning pipeline (see Methods and Fig. S23, ESI†). First, we model multi-dimensional chemical processes using early cycle and guiding sample data; second, we adapt these predictions to specific temperatures; and third, we use adapted chemical processes to avoid the need for physical measures in later cycles. The extent of early data used is tailored to meet the desired accuracy, assessed by mean absolute percentage error for consistent cross-stage comparisons.
In early cycles (first 10%), our method and model 2 both achieve a MAPE of 0.24%, while model 1 has a slightly higher error at 0.38%. Models 3 and 4, however, struggle with significant errors of 3.48% and 2.82%, respectively, highlighting difficulties with early temperature-induced lifetime deviations (see Fig. S24, ESI†). Notably, model 2 worsens in the last 10% of cycles, with MAPE of 5.82%, underscoring the importance of temperature consideration, which model 2 lacks. Despite initial similarities, IMVs become crucial in later stages, with model 2 showing a late-cycle MAPE of 5.62%. Our model remains robust and precise across all stages, peaking at a MAPE of 1.53% in the last 10% of cycles, demonstrating the efficacy of incorporating IMVs and physics knowledge to address temperature-induced long-term variations. Moreover, the error distribution of the proposed method is significantly lower than the benchmark models, strengthening its practical relevance, especially in quality assurance contexts where prediction performances in extreme cases matter most.
Our analysis extends to sensitivities across varying EOL capacity values for customized verification scenarios, focusing on the degradation path before reaching a specific capacity. Fig. 4d indicates that benchmark models perform worse as the target capacity decreases, underscoring the difficulty of projecting future degradation with initial data alone. Yet, our model consistently surpasses others, with a maximum deviation of 33 cycles, despite predictions being supervised thousands of cycles in advance. To enhance verification speed and computational efficiency, we explore the reduced data availability, showing in Fig. 4e that errors remain below 2% MAPE at both 35 and 45 °C with just 4.2% of lifetime data (50 cycles). The challenge of data scarcity, particularly with a limited number of parallel samples due to constraints in cost or time, was also assessed. A specific test using only high-temperature (55 °C) samples for accelerated verification demonstrates the impact of data paucity: a single sample results in high errors, but increasing to five samples significantly improves verification accuracy across various temperatures (Fig. 4f). In an ultra-early verification setting, prioritizing time over accuracy and utilizing the first 50 cycles, our model achieves average MAPEs of 4.9% across 25, 35, and 45 °C, outperforming benchmarks under similar data limitations (Table S4, ESI†). These findings affirm the viability of the proposed method in real-world verification contexts, offering adaptability in multi- and uni-source domain applications, and providing valuable insights for target domain evaluation with constrained data resources.28,36
We distinguish between kinetics and thermodynamics based on current stage densities, positing that machine learning-derived insights on thermodynamic loss enhance predictive accuracy at a single temperature while kinetic insights facilitate temperature adaptability. Group-wise analyses in Fig. 4g and h reveal a notable rise in the importance of capacity features in low-current areas versus their reduced significance at high currents, correlating with the observation that thermodynamic losses, not kinetic, predominantly affect degradation with a 79% share. Regarding other features, we note that the temperature impact on verification becomes negligible, indicating that physics-informed machine learning neutralizes temperature influence on predictive performance. Among these features, lumped resistance (RL), ohmic resistance (RO), and polarization speed (Vg) are prioritized for their contribution to verification accuracy. The contribution of Vg, influenced by SOC region sensitivities, is minimized due to its indirect relation to polarization resistance. RL and RO are more significant, incorporating concentration and ohmic polarization components. However, the challenges of prototype verification are dualistic since a satisfactory explanation of dominating loss types does not guarantee a good verification, rather, it also depends on temperature adaptability associated with kinetic behaviors, see Table S5 (ESI†). This is attributable to temperature primarily influencing kinetics, underlined by the Arrhenius law. Our model, predicated on this principle, reveals the expected diminished adaptability of thermodynamic responses to temperature changes. Thus, achieving a balanced verification requires weighing thermodynamic explanation capability against kinetic adaptability, as explored in Supplementary Note 5 and Table S6 (ESI†).
Contrary to bottom-up approaches that trace macro performance back to specific mechanisms, the proposed method employs a data-driven strategy to decouple loss types by correlating observable electrical signals with underlying thermodynamic and kinetic degradation processes, as illustrated in Fig. 5b. We utilize FEA to elucidate complex physical processes that occur internally during degradation by reproducing and visualizing the multi-step charging in Fig. S30–S32 (ESI†). Simulated degradation incorporating modeling of SEI thickening in Fig. 5a can be found in Supplementary Note 7 (ESI†). SEI thickening corresponds to LLI (thermodynamic loss) and contributes to increased impedance (kinetic loss), see Fig. S33 (ESI†). In Fig. S34a (ESI†), the dV/dQ response curve to equilibrium potential is pronounced at the onset of charging, as the battery must surmount energy barriers. While near the end of charging, the vacancies of materials are fully occupied by Li-ions, additional barriers are faced that account for a steeper dV/dQ curve gradient, making the initial and end of SOC represent thermodynamic characteristics.45 Moreover, switching between high and low current regions divides the process into thermodynamics and kinetics, see Fig. S34a and b (ESI†).
Fig. 5c illustrates that lithium-ion concentration varies across different charging steps, highlighting disparities between the initial and the 1000th cycles. In kinetic stages, lithium-ion concentrations exhibit a noticeable unevenness, while in thermodynamic stages, negligible concentration variation can be observed. Concentration polarization is increasingly pronounced at the 1000th cycle, and differences between charging stages are more evident, which evidences our featurization taxonomy by deliberately including dynamic information in current switching stages. Fig. 5d delves into total polarization changes across SOC regions, revealing significant increases during kinetic stages due to abrupt high current density shifts that challenge lithium transport and charge transfer capabilities, resulting in uneven lithium-ion distribution and internal particle lithiation (Fig. S30–S32, ESI†). Conversely, low current density stages exhibit less polarization, reflecting that thermodynamics is more significant than kinetics.
In Fig. 5e, we discern the interplay between concentration polarization and thermodynamic loss over a lifetime, observing an initial oscillation due to activation in early cycles that stabilizes into a clear dominance of thermodynamic loss and concentration polarization in the post-activation stage. Fig. 5f explores the correlation between these two degradation patterns across four temperatures, revealing consistent patterns that initial degradation shows a pronounced dip (marked by circle symbols), which becomes more profound and delayed at lower temperatures. This pattern aligns with activation processes including SEI layer formation and electrode structural change, impacting the primary degradation correlation. At lower temperatures, a temporary capacity restoration occurs (Fig. S24, ESI†), leading to a weaker correlation between concentration polarization and thermodynamic loss. At higher temperatures, quicker activation leads to a less dip, transitioning into a phase of predictable aging marked by SEI growth, increased LLI, and thus increased impedance.
As batteries progress to the later stages of their lifetime, another critical point (marked by square symbols) signifies a shift towards irreversible degradation, characterized by significant LAM and the accelerated degradation processes, as shown in Fig. 5a. This phase sees a mixture of degradation mechanisms, leading to a notable decline in the correlation between concentration polarization and thermodynamic loss, with this shift manifesting earlier at higher temperatures. Analyzing quantified SAGE across early, middle, and late phases (Fig. S35–S38, ESI†) reveals distinct aging behaviors at different lifecycle stages. Initially, capacity features fluctuate slightly, but as the battery ages and internal conditions worsen, changes in capacity and resistance features become evident. We note that such degradation patterns, elucidated through machine learning, correlate precisely with statistical predictions. Further, incremental capacity analysis of discharge curves (Fig. 5g and Fig. S39, ESI†) confirms the existence of severe LLI and LAM, evidenced by reduced peak intensity in low SOC areas (indicating LAM at the anode) and peak shifts (signifying LLI).46
This analysis underscores the intensification of battery degradation in later lifetime stages, notably with severe LAM under the high-temperature accelerated aging test. Benchmarking degradation patterns (Supplementary Note 8, ESI†) reveal distinct behaviors for thermodynamic and kinetic losses. Thermodynamic loss, averaging 85% of total degradation across temperatures, closely matches our 79% estimation for thermodynamic loss from machine learning interpretation (Fig. 5h). Polarization types, divided into concentration polarization and others, constitute an average of 82% of total polarization, corroborating with our 74% estimation from machine learning interpretation (Fig. 5i). Fig. S40 (ESI†) illustrates thermodynamic and kinetic loss contributions during discharge, where kinetic decay, indicated by impedance rise, can be mitigated by lowering current density. In contrast, thermodynamic loss represents irreversible LAM, persisting at a low current density.
Fig. 6 presents an assessment of refined direct recycling and other conventional (direct, hydro-, and pyro-) recycling, concerning the economic viability and environmental impact, see Supplementary Note 9 (ESI†). Refined direct recycling refers to a non-destructive diagnosis of the defective prototypes in the early stages, where lithium supplement is applied before structural defects occur. Fig. 6a shows that the refined direct recycling yields profit across all SOH levels, which can be rationalized by the saved time and cost of materials after the disassembly. Other methods, especially hydrometallurgy recycling, only become profitable with higher SOH. While the advantage of refined direct recycling in Fig. 6b marginally decreases with increasing SOH compared with other recycling methods due to the increased price of recycling products using conventional methods, the superiority of refined direct recycling is stable thanks to the simplified process and affordable lithium supplement price. Here we turn to amplifying the implication of refined direct recycling by incorporating the transport impact model (TIM), considering the interaction between production, the elasticity of vehicle sales, the penetration rate of EVs, and technological advancements, see Supplementary Note 10 (ESI†).
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Fig. 6 A technology-economic analysis of the scrap material recycling from defective prototypes using refined direct (ours), direct, hydrometallurgy (hydro-), and pyrometallurgy (pyro-) recycling methods, respectively. See Supplementary Note 9 (ESI†) for the methodology of the technology-economic analysis. (a) The unit profit and (b) incremental unit profit (refined direct recycling compared with baselines) comparison of different recycling methods, for both nickel manganese cobalt (NMC811) and lithium iron phosphate (LFP) batteries, considering SOH. (c) The total production, scrap rate, and scrap scale of new batteries (including NMC and LFP) from 2020 to 2060, derived from the transport impact model (TIM),48–50 see Supplementary Note 10 (ESI†) for the settings. (d) Annual and accumulated profit from recycling slightly degraded (95% SOH) batteries, calculated based on the production estimation of both NMC and LFP in (c). (e) Unit profit composition against SOH for LFP battery prototypes. (f) Unit environmental and energy impact of recycling slightly degraded NMC (95% SOH) prototype batteries, including volatile organic compounds (VOC), carbon monoxide (CO), nitrogen oxides (NOx), PM10, PM2.5, sulfur dioxide (SOx), black carbon (BC), organic carbon (OC), methane (CH4), nitrous oxide (N2O), and greenhouse gases (CO2). |
Fig. 6c forecasts battery production scale, scrap rate, and scrap scale over time from 2020 to 2060, showing a surge in scarp battery peaking circa 2035, reaching 230 million kg followed by a decline as advancements in production technology dampen the scrap rate to 0.38% by 2060. In this context, Fig. 6d shows the total projected profit over time by recycling defective prototype LFP and NMC battery at 95% SOH, aligning with the zenith of scrap amount depicted in Fig. 6c. The incremental profit, consequently, anticipates a surge before 2035 and a slowed incremental speed, thereafter, demonstrating an up to 19.76 billion USD scrap recycling market by 2060. We emphasize such a market can be notably larger due to the material diversities in next-generation prototype batteries and the stubbornly higher scrap rate than our estimation in the R&D stage. Fig. 6e depicts the unit profit composition at different SOH for LFP prototype batteries, demonstrating consistently higher revenues (15.64$ per kg) and lower costs (2.37–2.63$ per kg) stemming from its procedural efficiency by inflicting no structure repair requirements, or extra treatment reagents. In Fig. 6f, concerning the environmental and energy impact, the refined direct recycling for NMC prototype batteries exhibits superior performance in all environmental pollutants and energy use.
We prospect that our findings are material-agnostic, thus being widely applicable for promoting battery lifecycle sustainability in prototype manufacturing, electric vehicles, reuse, and recycling with minimized uncertainties, see Supplementary Discussion 1 (ESI†). The proposed physics-informed feature engineering and machine learning method are promising in balancing lifetime trajectory prediction efficiency and confidence by understanding electrochemical level behaviors that are hidden behind electric signals. Future research should expand to include more material compositions and chemistries to generalize findings, even to different battery technologies such as all-solid-state batteries. Addressing open challenges of electrochemical-level decoupling of degradation patterns could further consolidate the statistical evidence. Ultimately, this study shows the promise of non-destructive characterization using a data and electrochemistry fused method, paving the way for enhanced sustainability in future battery manufacturing, reuse, and recycling by investigating complex system evolutions with physics-informed learning.
|Uactual − Utheoretical(*)| = ΔE(SOC,SOH,T) + η(I,SOC,SOH,T) | (1) |
U actual is the actual working electrode voltage. Utheoretical is the theoretical open-circuit voltage reflective of the essential characteristics of the battery material as-manufactured prototypes, denoted by the * symbol. The ΔE is the thermodynamic voltage loss, attributed to the intrinsic material change due to aging, as a function of SOC, SOH, and environmental temperature T. η is the current-induced polarization, which can be further subclassified into three parts, e.g., activation polarization (ηact), ohmic polarization (ηohm), and concentration polarization (ηcon) as follows:
η = ηact + ηohm + ηcon | (2) |
This material agnostic formula quantifies the respective contributions of thermodynamic and kinetic losses to the overall battery degradation, with their relative proportions changing as a function of SOC, SOH, environmental temperature T, and applied current I.
Considering the cut-off voltage is a scalar vector for each battery, we deliberately broadcast dummy cycling indexes to span the cut-off voltage vector Um×9 to a cut-off voltage matrix U(C×m)×10 to predict continuous chemical process, where m is the battery number and C is the total length of cycling index of all batteries, equivalently the length of the entire lifetime. Given a feature matrix F(C×m)×N (see ESI† for more details on the featurization taxonomy), where N is the number of features, the model learns a composition of L intermediate layers of a neural network:
![]() | (3) |
The chemical process prediction model is trained on selected temperatures (i.e., temperatures where already measured data are accessible), while the temperature-related chemical process variations are considered using the physics-informed transferability. In each selected temperature, we split the data into 75% and 25% for training and testing, respectively. We train the chemical process prediction model using Adam optimizer, with epochs of 30 and a learning rate of 10−4. The loss function of the chemical process prediction model is:
![]() | (4) |
![]() | (5) |
![]() | (6) |
![]() | (7) |
![]() | (8) |
![]() | (9) |
![]() | (10) |
![]() | (11) |
The multi-source transfer based on ATscore includes the following three steps. Here we give an example for illustration. Detailed settings to reproduce the results in the manuscript are otherwise specified. First, we calculate aging rates r for all target and source domains by using early-stage data, i.e., we set start = 100, end = 200, n = 50 in eqn (8). After calculating aging rates for all features or aging curves, we obtain a target domain aging rate vector rtarget1×N and a source domain aging rate matrix rsourceK×N, where K and N are the number of source domains and the number of features, respectively. Second, we calculate the transferability metric ATscore and weight vector W1×K = {Wi} by eqn (6) and (10). Third, we predict the late stage (cycles after 200) aging rate of the target domain (rtarget) using eqn (11). Note that ATsourcei→targetscore and Wi are obtained by both target and source domain early-stage data, which are used to measure the transferability from source domain to target domain based on their aging rate similarity. risource is obtained from all accessible data in the source domain, consistent with our definition of the early-stage estimate problem. Specifically, only early-stage data in target domain is available in practice, while source domains can provide more comprehensive aging information to assist the target prediction using complete data. For multi-source domain adaptation, the source domain temperature is set to 25 °C, and 55 °C, and the target domain temperature is set to 35 °C, and 45 °C, for practical verification purposes that intermediate temperatures should be studied. For uni-source domain adaptation, the source domain temperature is set to 55 °C, and the target domain temperature is set to 25 °C, 35 °C, and 45 °C, for practical verification purposes that use accelerated data (55 °C) to rapidly verify battery performance under other temperatures.
![]() | (12) |
![]() | (13) |
![]() | (14) |
SAGEWini = SAGE(XWini,YWini) | (15) |
![]() | (16) |
The average of SAGE in all windows, i.e., across the entire lifetime, is defined as:
![]() | (17) |
![]() | (18) |
Footnotes |
† Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d4ee03839h |
‡ These authors were of equal contributions. |
This journal is © The Royal Society of Chemistry 2025 |