INTRODUCTION: The high incidences of both the developmental delay among young children and the mental health problems of their caregivers are major threats to public health in low-income and middle-income countries. Parental training interventions during early childhood have been shown to benefit early development, yet evidence on strategies to promote caregiver mental health remains limited. In addition, evidence on the optimal design of scalable interventions that integrate early child development and maternal mental health components is scarce. METHODS AND ANALYSIS: We design a single-blind, factorial, cluster-randomised controlled, superiority trial that will be delivered and supervised by local agents of the All China Womens Federation (ACWF), the nationwide, government-sponsored social protection organisation that aims to safeguard the rights and interests of women and children. We randomise 125 villages in rural China into four arms: (1) a parenting stimulation arm; (2) a caregiver mental health arm; (3) a combined parenting stimulation and caregiver mental health arm and (4) a pure control arm. Caregivers and their children (aged 6-24 months at the time of baseline data collection) are selected and invited to participate in the 12-month-long study. The parenting stimulation intervention consists of weekly, one-on-one training sessions that follow a loose adaptation of the Reach Up and Learn curriculum. The caregiver mental health intervention is comprised of fortnightly group activities based on an adaptation of the Thinking Healthy curriculum from the WHO. Primary outcomes include measures of child development and caregiver mental health. Secondary outcomes include a comprehensive set of physical, psychological and behavioural outcomes. This protocol describes the design and evaluation plan for this programme. ETHICS AND DISSEMINATION: This study received approval from the Institutional Review Board of Stanford University (IRB Protocol #63680) and the Institutional Review Board of the Southwestern University of Finance and Economics in Chengdu, Sichuan, China. Informed oral consent will be obtained from all caregivers for their own and their childs participation in the study. The full protocol will be publicly available in an open-access format. The study findings will be published in economics, medical and public health journals, as well as Chinese or English policy briefs. TRIAL REGISTRATION NUMBER: AEA RCT Registry (AEARCTR-0010078) and ISRCTN registry (ISRCTN84864201).

Layered iron/manganese-based oxides are a class of promising cathode materials for sustainable batteries due to their high energy densities and earth abundance. However, the stabilization of cationic and anionic redox reactions in these cathodes during cycling at high voltage remain elusive. Here, an electrochemically/thermally stable P2-Na_0.67Fe_0.3Mn_0.5Mg_0.1Ti_0.1O₂ cathode material with zero critical elements is designed for sodium-ion batteries (NIBs) to realize a highly reversible capacity of ≈210 mAh g^-1 at 20 mA g^-1 and good cycling stability with a capacity retention of 74% after 300 cycles at 200 mA g^-1, even when operated with a high charge cut-off voltage of 4.5 V versus sodium metal. Combining a suite of cutting-edge characterizations and computational modeling, it is shown that Mg/Ti co-doping leads to stabilized surface/bulk structure at high voltage and high temperature, and more importantly, enhances cationic/anionic redox reaction reversibility over extended cycles with the suppression of other undesired oxygen activities. This work fundamentally deepens the failure mechanism of Fe/Mn-based layered cathodes and highlights the importance of dopant engineering to achieve high-energy and earth-abundant cathode material for sustainable and long-lasting NIBs.