Operating High‐Energy Lithium‐Metal Pouch Cells with Reduced Stack Pressure Through a Rational Lithium‐Host Design

Abstract

cyclability under low-Li-excess and lean electrolyte conditions. [20][21][22] The formation of a stable, dense, atomically thin solid electrolyte interphase (SEI) is critical to suppress the depletion of metallic Li and liquid electrolytes. However, the relatively thin SEI usually undergoes a repeated fracture and rebuilding process over cycling. [23,24] Transitioning from liquid electrolytes to more stable inorganic solid electrolytes offers a potential pathway to enable highly reversible Li-metal anode. [7,25,26] Careful cell and material design of anode-free Li metal || NMC full cells based on sulfide solid electrolytes has enabled thousands of full cycles without degradation. [27] Though solid electrolytes, such as the sulfide-based electrolytes, are unstable with Li metal, parasitic interfacial reaction ceases when a kinetically stable interphase layer is formed. [27] Moreover, the solid electrolyte usually displays a high stiffness and good ductility than the porous separator in liquid electrolyte cells; therefore, it performs as mechanically strong support to prevent the fracture of the interphase layer. [27,28] Despite these efforts, the interface between the Li-metal anode and solid electrolyte suffers from chemomechanical degradation under practical cycling conditions (e.g., high current density). [29][30][31] First, the Li stripping reaction creates voids at the Li-metal/solid electrolyte interface, inducing a loss of ionic contact (Figure 1a). [32] Moreover, high-rate Li plating induces nonuniformity in the stress and electric fields, leading to heterogeneous Li plating, and further deteriorating the interfacial contacts. [33][34][35][36][37] An impractically high stack pressure (e.g., >1.0 MPa) is constantly required during cell operation to smooth the surface of the planar Li-metal anode. [38] With a stack pressure of above 1.0 MPa, most solid-state cells were tested with pressure jigs and a rigid sleeve to avoid the side effects of Li-metal creep in the radial direction. [39] The complicated cell design increases the manufacturing cost and dilutes the celllevel energy. In contrast, the optimized stack pressure adopted by scalable Li-ion pouch cells is usually within the range of 0.05-0.5 MPa. [40] The design of a 3D Li-metal anode potentially enables a mild stack pressure since the high surface area of the anode scaffold provides more intimate ionic contacts (Figure 1b). In addition, a small local current at the interface benefits the interface stability. [41][42][43][44][45] However, this direction has Transitioning from a liquid electrolyte to an inorganic solid electrolyte offers a potential pathway to enable highly reversible lithium-metal anodes. However, the solid-electrolyte-protected lithium-metal anode suffers from poor interfacial ionic contacts and requires an impractically high stack pressure (>1.0 MPa) to maintain the interfacial contacts. It is demonstrated here that combining a hollow silver/carbon fiber scaffold and an inorganic/ organic composite electrolyte enables a highly revers...

Insights into interfacial physiochemistry in sulfide solid-state batteries: a review

“…110,111 To maintain dense contact in traditional ASSBs, an extremely high stacking pressure is usually employed in the cell fabrication and cycling process. 105,112 However, for Li-based ASSBs, it is pivotal to search for reasonable stack pressure values that determine whether the battery can work efficiently. Low bulk pressure is not sufficient to achieve tight contact between interfaces while too high stack pressure might cause severe creeping of Li metal.…”

Working Principles of Lithium Metal Anode in Pouch Cells

“…The high-energy pouch-type LMBs can be operated with a reduced stack pressure through rational host design. [171] A pressure self-adaptable Li composite anode is able to regulate the Li plating/stripping behaviors inside the anodes. [25] The adaptive pressure generated from the elastic polymer filled inside the conductive host renders continuous electronic pathways inside the anodes and restricts the growth of Li dendrites.…”

Adaptive Multi‐Site Gradient Adsorption of Siloxane‐Based Protective Layers Enable High Performance Lithium‐Metal Batteries

“…[8] Additionally, the infinite volume expansion that occurs during cycling stimulates the creation of fissures in the SEI, exposing fresh Li to a lower energy barrier for Li-ion transport and exacerbating non-uniform deposition of Li. [9] Although the use of hosts [10][11][12][13] and mechanically resistant films [14][15][16] can inhibit dendrite formation, the unstable SEI remains a major barrier for LMA materials. In recent years, great efforts have been devoted to improving the stability of the LMA interface.…”

“…Although the use of hosts [ 10‐13 ] and mechanically resistant films [ 14‐16 ] can inhibit dendrite formation, the unstable SEI remains a major barrier for LMA materials. In recent years, great efforts have been devoted to improving the stability of the LMA interface.…”