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Sodium‐ion batteries (SIBs) are emerging as promising energy storage technologies, particularly for grid‐scale applications, due to their low material costs stemming from abundant natural resources. Meeting the increasing demand for higher energy density requires the development of innovative electrode and electrolyte materials, along with advanced analytical and fabrication techniques. However, the energy density of SIBs is often evaluated based solely on the capacities and cell voltages of active materials in half‐cell configurations, neglecting engineering considerations for full‐cell configurations. This study investigates the effects of electrode composition and the balance in capacities between positive and negative electrodes (N/P ratio) on the performance of full‐cell configurations, using Na3V2(PO4)3 (NVP) and hard carbon (HC) as representative electrode materials. Through a systematic analysis, an optimal composition for NVP and HC electrodes is proposed, considering areal capacity and capacity retention during full‐cell operations. Additionally, the importance of balancing the N/P ratio and the necessity of presodiation techniques to achieve high‐energy‐density SIBs are underscored. Overall, this work sheds light on key factors influencing the performance of SIBs and provides insights into strategies for enhancing their energy density and operational efficiency.

Abstract The automatic balancing mechanism introduced in 2004 aims to re-establish the financial equilibrium of the Japanese public pension systems. The non-linear functions for benefits embedded in the automatic balancing mechanism make it challenging to analyse the impact of market fluctuations on the adequacy of benefits and the sustainability of the pension system. Using a stochastic simulation model applied to the government’s public pension verification programmes, the risk of benefit levels and financial stability according to risk-taking in pension reserve funds for the Japanese public pension system is investigated. The Japanese public pension system is characterised by a pay-as-you-go system with substantial reserve funds. Benefit adequacy is measured by the replacement rate and financial sustainability by the reserve-to-expenditure ratio. The results show that for a high level of risk-taking in the reserve fund, the risk of benefits increases because the automatic balancing mechanism reduces benefits until the pension system recovers solvency. In addition, the risk of reserve funds increases because of the possibility of sizeable negative investment returns. In contrast, when risk-taking is low, the benefit level is locked in at a low level because investment returns are insufficient. Therefore, moderate risk-taking of reserve funds should be adequate.

Although prechamber (PC) is regarded as a promising solution to enhance ignition in lean-burn gas engines, a lack of comprehensive understanding of PC jet penetration dynamics remains. This study proposed a zero-dimensional (0D) model for PC jet penetration, considering the mixing of combustion products and unburned gases in jets and the floating ejection pressure. A combustion completion degree was defined by employing fuel properties and heat release to estimate the time-varying jet density. Pressure differences between the PC and the main chamber (MC) were referred to as the ejection pressure. Then, this model was validated against experimental data from a constant volume chamber (CVC) and a rapid compression and expansion machine (RCEM) with CH4-H2 blends at different equivalent ratios. Results showed that the proposed model can provide a good prediction in stationary and turbulent fields with the calibrated model coefficient. The overall jet penetration exhibits a t0.5 dependence due to its single-phase characteristic and the relatively lower density compared to the ambient gas in MC. The flame propagation speed and heat release in PC influence the combustion completion degree at the start of jet ejection. The mass fraction of burned gas in the ejected jet grows in response to the mixture equivalent ratio. Jet penetration is primarily driven by ejection pressure, with tip dynamics barely affected by the pressure difference after peaks. Tip penetration intensity rises with increasing fuel equivalent ratio and H2 addition, owing to the faster flame propagation. These findings can offer useful suggestions for model-based design and combustion model development for gas engines. [ABSTRACT FROM AUTHOR]