The global aim to move away from fossil fuels requires efficient, inexpensive and sustainable energy storage to fully use renewable energy sources. Thermal energy storage materials^1,2 in combination with a Carnot battery^3,4,5 could revolutionize the energy storage sector. However, a lack of stable, inexpensive and energy-dense thermal energy storage materials impedes the advancement of this technology. Here we report the first, to our knowledge, ‘trimodal’ material that synergistically stores large amounts of thermal energy by integrating three distinct energy storage modes—latent, thermochemical and sensible. The eutectic mixture of boric and succinic acids undergoes a transition at around 150 °C, with a record high reversible thermal energy uptake of 394 ± 5% J g⁻¹. We show that the transition involves melting of the boric acid component, which simultaneously undergoes dehydration into metaboric acid and water that dissolve into the liquid. Being retained in the liquid state allows the metaboric acid to readily rehydrate to re-form boric acid on cooling. Thermal stability is demonstrated over 1,000 heating–cooling cycles. The material is very low cost, environmentally friendly and sustainable. This combination of a solid–liquid phase transition and a chemical reaction demonstrated here opens new pathways in the development of high energy capacity materials.

摆脱化石燃料的全球目标需要高效、廉价和可持续的储能，以充分利用可再生能源。热能存储材料^1,2 与卡诺电池^3,4,5 相结合，可能会彻底改变储能领域。然而，缺乏稳定、廉价和能量密集的热能存储材料阻碍了该技术的进步。在这里，我们报告了第一种，据我们所知，“三峰”材料，它通过整合三种不同的能量存储模式——潜能、热化学和显能——协同储存大量热能。硼酸和琥珀酸的共晶混合物在 150 °C 左右发生转变，可逆热能吸收达到创纪录的 394 ± 5% J g⁻¹。我们表明，转变涉及硼酸成分的熔化，硼酸成分同时脱水成偏硼酸和水，然后溶解到液体中。保持液态使偏硼酸在冷却时很容易再水化以重新形成硼酸。热稳定性在 1,000 次加热-冷却循环中得到证明。该材料成本非常低、环保且可持续。这里展示的固-液相变和化学反应的这种组合为高能容量材料的开发开辟了新的途径。