The structures and components of solid electrolyte interphase (SEI) are extremely important to influence the performance of full cells, which is determined by the formulation of electrolyte used. However, it is still challenging to control the formation of high‐quality SEI from structures to components. Herein, we designed bisfluoroacetamide (BFA) as the electrolyte additive for the construction of a gradient solid electrolyte interphase (SEI) structure that consists of a lithophilic surface with C−F bonds to uniformly capture Li ions and a LiF‐rich bottom layer to guide the rapid transportation of Li ions, endowing the homogeneous deposition of Li ions. Moreover, the BFA molecule changes the Li+ solvation structure by reducing free solvents in electrolyte to improve the antioxidant properties of electrolyte and prevent the extensive degradation of electrolyte on the cathode surface, which can make a superior cathode electrolyte interphase (CEI) with high‐content LiF.
Lithium (Li) metal battery is considered the most promising next‐generation battery due to its low potential and high theoretical capacity. However, Li dendrite growth causes serious safety problems. Herein, the 15‐Crown‐5 (15‐C‐5) is reported as an electrolyte additive based on solvation shell regulation. The strong complex effect between Li+ ion and 15‐C‐5 can reduce the concentration of Li ions on the electrode surface, thus changing the nucleation, and repressing the growth of Li dendrites in the plating process. Significantly, the strong coordination of Li+/15‐C‐5 would be able to make them aggregate around the Li crystal surface, which could form a protective layer and favor the formation of a smooth and dense solid electrolyte interphase with high toughness and Li+ ion conductivity. Therefore, the electrolyte system with 2.0 wt% 15‐C‐5 achieves excellent electrochemical performance with 170 cycles at 1.0 mA cm−2 with capacity of 0.5 mA h cm−2 in symmetric Li|Li cells. The obviously enhanced cycle and rate performance are also achieved in Li|LiNi0.6Co0.2Mn0.2O2 (NCM622) full cells. The 15‐C‐5 demonstrates to be a promising additive for the electrolytes toward safe and efficient Li metal batteries.
The structure and components of solid electrolyte interphase (SEI) is crucial to direct the growth of lithium particles. However, it is hard to have control over them. Herein, an SEI that shares the properties of Li2CO3‐rich and LiF‐rich types is realized by using different fluorine phenylphospines, and constructing a Li2CO3/LiF‐rich heterostructured SEI by using tris(4‐fluorophenyl)phosphine (TFPP) as the electrolyte additive. The well‐balanced SEI formed in TFPP‐containing electrolyte has the fast Li+ transport kinetics of Li2CO3, good electron insulator capability of LiF, and strong affinity toward Li+. It can effectively guarantee fast, uniform Li+ flux through the SEI while preventing electrons from the Li anode entering into SEI, and thus realizes uniform and dense Li deposition at the SEI/Li interface. As expected, the Li anode with TFPP‐containing electrolyte achieves a stable Li plating/stripping over 400 h at 1mA cm−2 while the full cell with a high‐voltage LiNi0.6Co0.2Mn0.2O2 cathode also enables long‐term stability with a capacity retention (87.8% after 200 cycles) at 0.1 A g−1 and excellent rate performance.
In this work, we synthesized N, F, P ternary doped macroporous carbon fibers (NFPC) for the first time and it exhibits efficient electrocatalytic activity as a bifunctional catalyst for ORR, OER and Zn-air batteries.
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