Development of new rechargeable batteries with superconcentrated electrolytes

严重的安全问题目前正在阻碍锂/钠电池的大规模使用。传统的电解质是高度易燃和易挥发的，这可能导致灾难性的火灾或爆炸。在电解质中引入阻燃溶剂的努力通常会导致电池性能下降，因为这些溶剂不能适当地钝化碳质阳极。我们提出了一种盐浓电解质设计，通过在阳极上形成坚固的无机钝化膜来解决这一难题。我们证明了一种使用盐和一种流行的阻燃溶剂（磷酸三甲基）的浓缩电解质，在没有任何添加剂或软粘合剂的情况下，实现了硬碳和石墨阳极的稳定充放电循环，循环次数超过1000次（超过一年），降解可以忽略；这一性能与传统的可燃碳酸盐电解质相当或优于。浓缩电解液不同寻常的钝化特性及其灭火特性有助于开发安全耐用的电池，并为开发更高能量密度的电池打开了限制。此外，我们发现这种浓缩的电解质有可能使电池在-20到100°C的范围内工作。

Severe safety concerns are currently impeding the large-scale employment of lithium/sodium batteries. Conventional electrolytes are highly flammable and volatile, which may cause catastrophic fires or explosions. Efforts to introduce flame-retardant solvents into the electrolytes have generally resulted in compromised battery performance because those solvents do not suitably passivate carbonaceous anodes. We propose a salt-concentrated electrolyte design to resolve this dilemma via the formation of a robust inorganic passivation film on the anode. We demonstrated that a concentrated electrolyte using a salt and a popular flame-retardant solvent (trimethyl phosphate), without any additives or soft binders, realized stable charge-discharge cycling of both hard carbon and graphite anodes for more than 1000 cycles (over one year) with negligible degradation; this performance is comparable or superior to that of conventional flammable carbonate electrolytes. The unusual passivation character of the concentrated electrolyte coupled with its fire-extinguishing property contributes to developing safe and long-lasting batteries, and unlocking the limit toward development of much higher energy-density batteries. Moreover, we found that this concentrated electrolyte potentially enables the battery operation from -20 to 100 °C.