Rational design of low interfacial resistance between NiS2 cathode and electrolyte for high-performance Li thermal battery

Abstract

As one of the main components of the cathode and electrolyte for Li thermal batteries (LTBs), conventional binders typically employ high thermal stability MgO to maintain LTBs structure stability, but MgO has the disadvantage of high resistance, which can result in a high resistance at the cathode-electrolyte interface. Thus, it is crucial to optimize the cathode-electrolyte interface for NiS2 to achieve high performance LTBs. Herein, Li7La3Zr2O12 (LLZO) with high thermal stability and excellent ionic conductivity was adopted in the cathode and electrolyte to replace the conventional binders, aiming to build a low resistance interface between the cathode and electrolyte, promoting the Li+ transport kinetics. More importantly, LLZO also plays a vital role in reducing molten salt leakage and enhancing the stability of the cathode-electrolyte interface in LTBs, which contributed to increasing the discharge capacity of the NiS2 cathode material. Consequently, LTB containing LLZO delivers a high discharge specific capacity of 635.1 mAh g−1 with a cut off voltage of 1.4 V at 100 mA cm−2 at 500 °C, retaining 72.8 % of the theoretical capacity of NiS2, which is 25.5 % higher than LTB with MgO. These findings indicate that optimizing the NiS2 electrode and LLZO electrolyte interface would be an effective way to enhance the performance of LTBs.