The future Internet-of-Everything (IoE), supported by the 6G and beyond wireless networks, will include battery-less intermittent computing (internet-of-things) IoT devices that use energy-harvesting power to support heterogeneous applications in diverse domains like smart-city, smart-infrastructure, environment-monitoring, and disaster scenarios. These devices need to operate sustainably in scarce-intermittent energy conditions and challenging environments. Energy buffers, implemented using small capacitors, support the execution of tasks like sense, send, receive, and control, that are associated with the concerned user-applications. In this article, we identify the end-user application support requirements and associated elements in intermittent computing IoT device network systems. We also discuss a multi-facet framework for sustainable operation of a battery-less IoT device network using application-aware federated charging controller based energy harvesting (AFCH) and energy-aware task scheduler with peripheral control (EASP). We describe the EASP with AFCH scheme for the battery-less IoT device operation to provide an improved application support. We conclude with a battery-less IoT device (with solar energy harvesting) case study that evaluates the peripheral (component) availability, initial-to-available time, and supported application rate in this context.