Research on the growth and inhibition of lithium dendrites in all-solid lithium batteries

Recently, Fang Qianfeng, a researcher at the Institute of Internal Friction and Solid Defects, Institute of Solid Physics, Hefei Academy of Material Sciences, Chinese Academy of Sciences, designed a solid-state battery with an asymmetric structure to study the deposition and transfer of lithium ions in solid-state batteries. The growth and suppression mechanism of lithium dendrites in Lithium Batteries is an important reference. Related research results are published in the Journal of power sources with the title "Intragranular growth and evenly distribution mechanism of Li metal in Li7La3Zr2O12 electrolyte".

Maintenance Free Battery Lithium Iron Phosphate Battery have high energy density, strong stability and long cycle life, and are widely used as a commercial and efficient energy storage device. However, due to the use of flammable organic electrolytes in commercial LiFePO4 Battery, when the battery is in a state of high temperature, short circuit, overcharge or physical damage, it is very likely to cause fire or even explosion. Therefore, the use of non-flammable inorganic solid electrolyte instead of liquid electrolyte is one of the most effective methods to solve the safety problem of lithium batteries. However, because lithium ions spontaneously form dendritic lithium dendrites during the deposition of the negative electrode, their sharp structures are prone to pierce the separator, causing the battery to short-circuit and posing potential safety hazards. Therefore, using an inorganic solid electrolyte instead of a liquid organic electrolyte and effectively inhibiting the growth of lithium dendrites during charging and discharging can better solve the safety problem of lithium-ion batteries and correctly understand the deposition and transfer of lithium ions in solid LiFePO4 Battery.

For this purpose, a solid-state battery with an asymmetric structure was constructed by making the lithium metal electrodes on both sides of the electrolyte perpendicular to each other (Figure 1a), and the lithium ion transport in the electrolyte was inferred by observing the state of lithium deposition on the electrolyte process. At the same time, the Au atomic layer was sputtered in the central area of the electrolyte surface layer, and compared with the area of the unsputtered Au atomic layer, the influence rule of the Au atomic layer on the deposition of lithium ions was obtained. The research results show that the electron distribution state of the electrolyte surface layer directly affects the transmission path of lithium ions in the electrolyte (Figure 1b), so that the lithium ions from the upper surface of the electrolyte are divergently transported in the electrolyte. Further analysis showed that in the unsputtered Au sputtering area, the lithium ion deposition showed an irregular distribution and distribution state (the left area in the blue frame in Figure 1a), which would induce the growth of lithium dendrites and induce short circuits. In the area where the Au atomic layer is sputtered, the lithium ion deposition appears as a uniform spherical particle distribution (the area in the red frame and the right area in the blue frame in Figure 1a), which effectively suppresses the lithium ions caused by the growth of lithium dendrites. The development of this work provides a theoretical and experimental basis for optimising the interface performance and safety performance of the all-solid battery.

The research was supported by the National Natural Science Foundation of China and the Natural Science Foundation of Anhui Province.