Colossal barocaloric effects in the complex hydride Li₂B₁₂H₁₂

Traditional refrigeration technologies based on compression cycles of greenhouse gases pose serious threats to the environment and cannot be downscaled to electronic device dimensions. Solid-state cooling exploits the thermal response of caloric materials to external fields and represents a promising alternative to current refrigeration methods. However, most of the caloric materials known to date present relatively small adiabatic temperature changes (|∆T| ∼ 1 K) and/or limiting irreversibility issues resulting from significant phase-transition hysteresis. Here, we predict the existence of colossal barocaloric effects (isothermal entropy changes of |∆S| ∼ 100 JK⁻¹kg⁻¹) in the energy material Li₂B₁₂H₁₂ by means of molecular dynamics simulations. Specifically, we estimate |∆S| = 387 JK⁻¹kg⁻¹ and |∆T| = 26 K for an applied pressure of P = 0.4 GPa at T = 475 K. The disclosed colossal barocaloric effects are originated by an order-disorder phase transformation that exhibits a fair degree of reversibility and involves coexisting Li⁺ diffusion and (BH)⁻₁₂² reorientational motion at high temperatures.