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Transition-metal compounds (oxides, sulfides, hydroxides, etc.) as lithium-ion battery (LIB) anodes usually show extraordinary capacity larger than the theoretical value due to the transformation of LiOH into Li2O/LiH. However, there has rarely been a report relaying the transformation of LiOH into Li2O/LiH as the main reaction for LIBs, due to the strong alkalinity of LiOH leading to battery deterioration. In this work, layered silicate MgAl saponite (MA-SAP) is applied as a −OH donor to generate LiOH as the anode material of LIBs for the first time. The MA-SAP maintains a layered structure during the (dis)charging process and has zero-strain characteristic on the (001) crystal plane. In the discharging process, Mg, Al, and Si in the saponite sheets become electron-rich, while the active hydroxyl groups escape from the sheets and combine with lithium ions to form LiOH in the “caves” on sheets, and the LiOH continues to decompose into Li2O and LiH. Consequently, the MA-SAP delivers a maximum capacity of 536 mA h·g–1 at 200 mA·g–1 with a good high-current discharging ability of 155 mA h·g–1 after 1000 cycles under 1 A·g–1. Considering its extremely low cost and completely nontoxic characteristics, MA-SAP has great application prospects in energy storage. In addition, this work has an enlightening effect on the development of new anodes based on extraordinary mechanisms.

Anode materials with simultaneously large capacity and low working voltage have always been one of the pursuing goals in the development of lithium-ion batteries. In this report, erdite NaFeS2 was synthesized by phase conversion of Fe-saponite for the first time, which displays attractive lithium-storage performance as an anode material. Taking into consideration that NaFeS2 can be regarded as sodium pre-embedded FeS2, a thorough comparison of lithium-storage performance between NaFeS2 and FeS2 was carried out. Theoretical calculation reveals that NaFeS2 has metallic conductivity and thus faster electron transfer than FeS2. The main oxidation and reduction peaks of the NaFeS2/Li battery reduce by 0.4–0.8 V compared with those of FeS2/Li, which are qualitatively supported by density functional theory calculations. Additionally, NaFeS2 delivers higher capacity, longer cycle life (1157 mAh·g–1 after 500 cycles), and better rate performance (618 mAh·g–1 at 5 A·g–1) than FeS2. Significantly decreased (de)­lithiation voltage and increased capacity through changing the electrochemical reaction mechanism are favorable for improving the energy and power density of the batteries. This work develops a facile method of transforming silicate into sulfide and puts forward a strategy to reduce the (de)­lithiation voltage of high-capacity anode materials, which is meaningful for boosting energy/power densities of energy storage devices.

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