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The dual‐ion battery (DIB) is a promising energy storage system that demonstrates high‐power characteristics and fast‐charging capability. However, conventional electrolytes are not compatible with the high‐voltage graphite cathode and the reactive Li metal anode, thus leading to the poor cycle stability and low Coulombic efficiency of the DIB. Here, an all‐fluorinated electrolyte is reported that can enable a highly stable operation of the graphite||Li DIB up to 5.2 V by forming robust and less‐resistive passivation films on both electrodes to reduce side reactions. The electrolyte allows reversible PF6– anion insertion/extraction and Li+ cation plating/stripping in the graphite||Li battery, achieving stable cycling with 94.5% capacity retention over 5000 cycles at 500 mA g–1, high capacity utilization of 91.8% of the available charge capacity at 50 C (5000 mA g–1), and also minimal self‐discharge. At a low temperature of 0 °C, this all‐fluorinated electrolyte exhibits 97.8% of the room temperature reversible capacity, along with ≈100% capacity retention after more than 3000 cycles, at 5 C. This work sheds a new light on the development of fluorinated electrolytes for high voltage and long‐lasting DIBs. [ABSTRACT FROM AUTHOR]

Dual-ion batteries (DIBs), well-known for the high-rate capability of the graphite cathode, urgently need a suitable anode material to realize their high power density in practical applications. In that respect, Li 4 Ti 5 O 12 (LTO), which can be cycled at high rates for thousands of cycles, can be a good candidate. However, a facile method to stabilize the graphite||LTO full cells is necessary. Herein, we introduce LiDFOB additive into the electrolyte of graphite||LTO cells, which drastically improves the cycling performance and reduces self-discharge of the DIBs. Specifically, by adding 1.0 wt% LiDFOB to 2 M LiPF 6 in fluorinated ethyl methyl carbonate, graphite||LTO DIBs can maintain stable charge-discharge for over 8000 cycles at 20 C. Characterizations indicate that LiDFOB forms a robust LiF-rich solid electrolyte interphase (SEI) on the LTO anode to suppress side reactions such as electrolyte decomposition and gas generation. LiDFOB additive forms a thin LiF-rich SEI on Li 4 Ti 5 O 12 (LTO) anode, successfully hinders the further decomposition of LiPF 6 and electrolyte. As a result, stable cycling of graphite||LTO dual-ion full batteries is extended to over 8000 cycles. [Display omitted] • Graphite.||LTO dual-ion batteries with stable capacity for 8000 cycles are achieved • LiDFOB additive improves cycle and rate performances of graphite.||LTO batteries • A LiF-rich SEI is formed in-situ on the LTO anode with LiDFOB additive. • The LiF-rich SEI on LTO suppresses side reaction and electrolyte decomposition. [ABSTRACT FROM AUTHOR]