At present, aqueous lithium-ion batteries (ALIB) based on neutral aqueous electrolytes are attracting attention due to their inherent high safety, environmental friendliness, and ease of manufacturing. However, the electrochemical stability window for water molecules is extremely limited (123 v .SHE,25, pH = 7,1 atm) and a severe hydrogen evolution reaction (HER) at the negative electrode interface beyond the window severely limits the high pressure (>1.).5 v) the development of aqueous batteries, which limits the energy density of aqueous batteries. From the existing commercial lithium-ion batteries, it can be seen that the effective strategy of inhibiting HER can be achieved by forming a strong solid electrolyte interface (SEI) film at the surface of the negative electrode to passivate the negative electrode, because the strong SEI protective layer successfully blocks the mutual contact between the water molecules and the negative electrode, effectively preventing the decomposition of continuous water molecules, which can expand the electrochemical window of the aqueous electrolyte beyond the thermodynamic window constraints of the aquatic electrolyte. However, compared with commercial anhydrous organic electrolytes, it is more challenging to efficiently construct high-quality and stable SEIs from aqueous electrolytes.
Spatio-temporal synchronization" design idea of in-situ construction of SEI.
Figure 1(a) Schematic diagram of the construction mechanism of traditional and "spatiotemporal synchronization" SEIs (Figure: Chemical validation of LIPO generation); (b) SEI generation efficiency (SFE) calculated from the electron utilization of the side reaction; (c) Solubility of the main components in the SEI of aqueous lithium-ion batteries in pure water.
Figure 2: Verification of "spatiotemporal synchronization" in-situ construction of rich Lipo-SEI.
Based on this, Zhu Xiangzhen, a doctoral student from the HE-E01 Group of Huairou Research Department of Beijing National Research Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Academician Chen Liquan and Researcher Suo Liumin of Beijing Clean Energy Frontier Research Center, proposed a strategy to construct a solid SEI through chemical precipitation and electrochemical reduction. By adding LiHPO as a film-forming additive to the TiO anode, according to the principle of HPO** ionization equilibrium movement, the OH produced by HER was captured at the anode interface by chemical method, and the HPO equilibrium shifted to the right, and intelligently grew at the active site of hydrogen evolution, and finally a stable LiPO-rich SEI protective layer was successfully constructed on the surface of the Tio anode.
Figure 3Electrochemical performance of LMO tio@x% LHPO (X and 10 whole cells (P-N mass ratio of 2:1).
Based on the SEI construction strategy of "spatiotemporal synchronization", the formation of Lipo in the 10M LITFSI electrolyte with a high water content (>25%) can effectively prevent the precipitation of the negative electrode H without additional consumption of LI and electrons from the positive electrode, thereby reducing the threshold of the salt concentration of the aqueous electrolyte required for high-voltage aqueous lithium-ion batteries, and providing a new direction for realizing the low-salt concentration-dependent interfacial chemistry of aqueous batteries.
Figure 4SEI Formation Mass (SFQ) of LMO tio@5% LHPO whole cell during the first two cycles in 10 M LITFSI.
The work was published in the internationally renowned journal Angewandte under the title of "Highly Efficient Spatially Temporally Synchronized Construction of Robust Li3PO4-Rich Solid Electrolyte Interphases in Aqueous Li-ion Batteries". Chemie International Edition. Corresponding author: Prof. Suo Liumin, first author: Dr. Zhu Xiangzhen.
Figure 5LMO tio@5% LHPO full cell at 0After 10 cycles at a current density of 5C, a Lipo-rich SEI is formed on the surface of the anode.
This work was supported by the National Key R&D Program of China (2022YFB2404500), the National Natural Science Program of China (U22B20124), the Young Talents Program of the Chinese Academy of Sciences, the Institute of Physics of the Chinese Academy of Sciences, the Beijing National Research Center for Condensed Matter Physics, the Beijing Clean Energy Frontier Research Center, the Huairou Clean Energy Materials Testing and Diagnosis and R&D Platform, the Beijing Advanced Innovation Center for Materials Genetic Engineering, and the Yangtze River Delta Physics Research Center.
Figure 6Electrochemical performance of LMO tio@5% LHPO whole cell in 10 M LiTFSI electrolyte.
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