Study On The Regulation Mechanism Of Lithium Lanthanum Zirconium Tantalum Oxide Coating On The Solid Electrolyte Intermediate Phase On The Surface Of Silicon-carbon Anod

Lithium-ion batteries have been widely used in electric vehicles and electronic products due to their high energy density,long cycle life and light weight.The anode material of lithium ion battery plays a key role in the energy density of the battery.Currently,graphite is used as the anode material for commercial lithium ion batteries.However,graphite has a low theoretical specific capacity(372 m Ah g-1),which is not enough to meet the needs of high-performance batteries.To improve the energy density of lithium-ion batteries,researchers are devoted to developing anode materials with high theoretical specific capacity.Silicon(Si)is regarded as one of the most promising anode materials for lithium ion batteries due to its high theoretical specific capacity(3579 m Ah g-1),high safety and abundant reserves.However,during the Li-ion deintercalation processes,the Si electrode suffers from a large volume change,resulting in the rupture of its structure and solid electrolyte interface(SEI),and then leading to a large capacity loss.In recent years,researchers have focused on the development of novel nanostructures to buffer their volume changes,but few studies have been reported on regulating the SEI composition on the surface of Si anodes.Therefore,we propose a method to control the surface SEI composition of silicon carbon(Si/C)anode using Li6.4La3Zr1.4Ta0.6O12(LLZTO)solid electrolyte,and study the electrochemical performance of the Si/C batteries and regulation mechanism of this method.The main results obtained are as follows:(1)PP-LLZTO separators with different coating thickness and number of coating surfaces were prepared by coating LLZTO layer on the polypropylene(PP)separator surface.It was found that the introduction of the LLZTO layer improved the wettability of the separator to the electrolyte,thereby improving the ion transport capacity of the separator.In addition,since the LLZTO layer could adsorb anions in the electrolyte,the ionic conductivity of the electrolyte is further improved.(2)The cycling stability of Li-Si/C cells and LFP-Si/C cells assembled with PP separators and PP-LLZTO separators with different coating thicknesses was investigated.It was found that the Li-Si/C cell and LFP-Si/C cell assembled by a PP-LLZTO separator coated with a thickness of 10 μm(PP-10 μm-LLZTO separator)exhibited the best cycling stability.Using PP-10 μm-LLZTO separator,the Li-Si/C cell exhibited a reversible specific capacity of 876 m Ah g-1 with capacity retention of 81% after more than 200 cycles at a current density of 450 m A g-1,and the Si/LFP cell delivered a reversible specific capacity of 125 m Ah g-1 with capacity retention of 91.8% after 100 cycles at current density of 53 m A g-1.(3)PP separators coated with the 10 μm thickness of Al2O3(PP-10 μm-Al2O3)and Zr O2(PP-10 μm-Zr O2)are prepared by the blade coating method,and the cycling performance of Li-Si/C cells assembled with PP-10 μm-LLZTO,PP-10 μm-Al2O3 and PP-10 μm-Zr O2 separators was compared.It was found that the Li-Si/C cell assembled by the PP-LLZTO separator exhibits the best excellent cycling performance.Using SEM and XPS characterization,the effect of PP-10 μm-LLZTO separator on Si/C anode was explored.Due to the regulation effect of LLZTO,more inorganic phases are formed on the surface of Si/C by SEI,which prove that the LLZTO layer plays a role in regulating the composition of SEI on the surface of Si/C anodes.