Systems and methods for storing and retrieving thermo-mechanical energy are disclosed. The systems and methods include a thermodynamic cycle (e.g., a reversible transcritical, trilateral, Brayton or Rankine/vapor compression cycle) that includes a plurality of loops and works as a heat pump in charging mode and as a heat engine in discharging mode. Each loop in the thermodynamic cycle includes pressure increasing and decreasing devices, high and low pressure heat exchanging devices, and the same or different working fluid. The system further includes one or more heat storage chains with hot and cold storage reservoirs and a heat storage fluid. At least one of the high and low pressure heat exchanging devices is a gradient heat exchanging device that exchanges heat with the heat storage chain. Also, at least one other high or low pressure heat exchanging device exchanges heat with a separate heat storage device or a heat source or sink.