To investigate the alternatives to lithium-ion batteries, potassium-ion batteries have attracted considerable interest due to the cost-efficiency of potassium resources and the relatively lower standard redox potential of K⁺/K. Among various alternative anode materials, hard carbon has the advantages of extensive resources, low cost, and environmental protection. In the present study, we synthesize a nitrogen-doping hard-carbon-microsphere (N-SHC) material as an anode for potassium-ion batteries. N-SHC delivers a high reversible capacity of 248 mAh g⁻¹ and a promoted rate performance (93 mAh g⁻¹ at 2 A g⁻¹). Additionally, the nitrogen-doping N-SHC material also exhibits superior cycling long-term stability, where the N-SHC electrode maintains a high reversible capacity at 200 mAh g⁻¹ with a capacity retention of 81% after 600 cycles. DFT calculations assess the change in K ions’ absorption energy and diffusion barriers at different N-doping effects. Compared with an original hard-carbon material, pyridinic-N and pyrrolic-N defects introduced by N-doping display a positive effect on both K ions’ absorption and diffusion.

In recent years, atomic-doping has been proven to significantly improve the electrochemical performance of biomass-derived carbon materials, which is a promising modification strategy. Among them, there are relatively few reports about O-doping. Here, porous carbon derived from orange peel was prepared by simple carbonization and airflow-annealing processes. Under the coordination of microstructure and surface groups, the derived carbon had excellent electrochemical performance for the K-ion batteries’ anode, including a high reversible specific capacity of 320.8 mAh/g, high rate performance of 134.6 mAh/g at a current density of 2000 mA/g, and a retention rate of 79.5% even after 2000 long-term cycles, which shows great application potential. The K-ion storage mechanisms in different voltage ranges were discussed by using various characterization techniques, that is, the surface adsorbed of K-ionswas in the high-potential slope area, and the intercalation behavior corresponded to the low-potential quasi-plateau area. In addition, the density functional theory calculations further confirmed that O-doping can reduce the adsorption energy barrier of K-ions, change the charge density distribution, and promote the K-ion storage. In particular, the surface Faraday reaction between the C=O group and K-ions plays an important role in improving the electrochemical properties.

Sodium-ion batteries are promising for cost-sensitive and low-temperature electric-vehicle applications, yet reliable battery management systems (BMSs) require evaluation beyond a development cell. This study develops a lightweight multi-task gated recurrent unit (GRU) framework that integrates timestep-level state-of-charge (SOC) estimation with window-based, cycle-informed state-of-health (SOH) estimation. The main A6 configuration uses aging-sensitive descriptors and contains 24,882 trainable parameters. On the NFM source-domain test set, A6 achieves 1.078% SOC root-mean-square error (RMSE), 0.978% cycle-aggregated SOH RMSE, and an SOH coefficient of determination (R²) of 0.835, compared with 2.409% SOH RMSE for the constant-mean baseline. An ablation analysis distinguishes the effects of task coupling and input observability. A separate three-input source-trained backbone is evaluated for external SOC transfer: on Hina, zero-shot RMSE is 22.5–36.2%, and calibration with 25% of the target cell’s 25 °C records reduces errors at unseen temperatures to 14.0–27.4%; on the CVUT 4S11P cold-start battery pack, zero-shot RMSE of approximately 27–29% decreases to 12.0–19.7% following adaptation on the first 25% of time-ordered records. The separate source-domain and transfer tests show why low in-domain error alone cannot establish SOC accuracy on a different commercial cell or battery pack, even when limited target-domain calibration is available.