Stack Pressure Considerations for Room‐Temperature All‐Solid‐State Lithium Metal Batteries

Abstract

All-solid-state batteries are expected to enable batteries with high energy density with the use of lithium metal anodes. Although solid electrolytes are believed to be mechanically strong enough to prevent lithium dendrites from propagating, various reports today still show cell failure due to lithium dendritic growth at room temperature. While cell parameters such as current density, electrolyte porosity and interfacial properties have been investigated, mechanical properties of lithium metal and the role of applied stack pressure on the shorting behavior is still poorly understood. Here, we investigated failure mechanisms of lithium metal in all-solid-state batteries as a function of stack pressure, and conducted in situ characterization of the interfacial and morphological properties of the buried lithium in solid electrolytes. We found that a low stack pressure of 5 MPa allows reliable plating and stripping in a lithium symmetric cell for more than 1000 hours, and a Li | Li6PS5Cl | LiNi0.80Co0.15Al0.05O2 full cell, plating more than 4 µm of lithium per charge, is able to cycle over 200 cycles at room temperature. These results suggest the possibility of enabling the lithium metal anode in all-solid-state batteries at reasonable stack pressures.

Toward Higher Voltage Solid‐State Batteries by Metastability and Kinetic Stability Design

“…[ 8 ] It is known that only a low testing pressure (a few MPa) can be applied to such lithium metal anode, as higher pressures will cause the mechanical short, and the initial contact between Li 3 PS 4 ‐coated Li and electrolyte is good enough without external pressure. [ 16 ] The battery was then tested in normal Swagelok cells with a negligible external pressure of only a few MPa, giving a quasi‐isobaric battery testing condition. In addition, one battery assembly of LGPS+C/LGPS/graphite‐Li was initially pressed at 467 MPa and then tested in a homemade pressurized cell with the applied external pressure calibrated as 250 MPa when fastening the battery, enforcing a quasi‐isovolumetric battery testing environment.…”

“…Many studies have correlated the electrochemical performance of solid‐state battery, especially ionic conductivity, with stacking pressure and obtained new understandings of the system. [ 15–20 ] Previously, we showed that mechanical constrictions, in the form of core–shell morphologies, could induce metastability in an expanded voltage range for both LGPS and LSPS. [ 8,21–23 ] In this work, we utilize cell‐level mechanical constrictions to better understand the nature of LGPS decay when charged to high voltages in full cell architectures.…”

Sulfide and Oxide Inorganic Solid Electrolytes for All-Solid-State Li Batteries: A Review

“…Kasemchainan et al [200] studied the effect of the current density (0.1-4.0 mA cm −2 ) and pressure (3 and 7 MPa) on Li|Li 6 PS 5 Cl|Li. Recently, Doux et al [201] Figure 7(1). It was observed that at the stack pressure of 5 MPa, no short-circuit occurred for up to 1000 h; moreover, the capacity retention of the cell was 81% after 100 cycles (Figure 7(2)).…”

“…(viii) Kasemchainan et al [200] and Doux et al [201] reported the critical current density limits for Li plating on Li 6 PS 5 Cl and studied the stack pressure limits of Li 6 PS 5 Cl, respectively.…”

Advanced Characterization Techniques for Interface in All‐Solid‐State Batteries

“…Insufficient contact area results in small contact area of interface, leading to large impedance in ASSBs. [ 39,40 ] It may also give nonuniformity of electric potential at the interface, accelerating the growth of metallic dendrite during cycle process and hence causing the final failure of ASSBs. [ 41 ] Undesirable interfacial side reactions may increase the impedance in ASSBs because the by‐products of the side reactions distributing at the interface usually have low ionic conductivity.…”