Thermal batteries: Can the max temp inside a battery be greater than the heat pump max operating temp?

Question

I'm curious about thermal batteries,

Let's say I have a heat pump with an maximum operating temperature of 100 °C, that is to say, the heat pump can "collect" thermal energy and heat its refrigerant to 100 °C. Now that we have "collected" the heat from the ambient source, we want to store it in some thermal sink.

Let's assume ambient is 23 °C, so the heat pump has "boosted" the temperature quite a bit, but in order to maximize our thermal sink lets assume desired temps inside the battery are in excess of 400° C, much more than our heat pump can deliver.

As I understand it, if we dumbly pump our 100 °C refrigerant into a heat exchanger inside the battery we are essentially presenting the battery with a cooler source than the battery's operating temp.

I assume:

1. When the battery is empty we could successfully heat it to nearly 100 °C with this heat pump, but not more.
2. If the battery was already at temp (400 °C), pumping the 100 °C source into it would actually heat the source, thus adding energy from the battery to the source / removing energy from the battery or "discharging" it.

The question is

1. Are my assumptions above correct?
2. Does the heat pump in this scenario really have to handle refrigerants that can handle temp ranges at or above the battery's max temp?
3. Is there such a thing as a thermal one way value? Something that would allow any energy entering the battery, regardless of temp, to add to the battery? I assume the heat pump itself is as close we can get to this, but maybe there is some other technology I don't know about.
4. Are the groups chasing this technology (thermal batteries) likely simply using thermal loops at the target battery temp? Or perhaps there are ways to chain heat pumps together that can further boost the temp prior to entering the battery.

Answer 1

Heat moves only from hot to cold.

To get heat to move from cold to hot you need a machine. That is what air conditioners and heat pumps do, move heat from cold to hot.

Certainly if you really needed high temperatures you could have a second (or multiple) heat pump that raised the temperature again, but understand the losses you get every time you use a machine to do something.