Sandwich, Vertical‐Channeled Thick Electrodes with High Rate and Cycle Performance

Abstract

3D thick electrode design is a promising strategy to increase the energy density of lithium-ion batteries but faces challenges such as poor rate and limited cycle life. Herein, a coassembly method is employed to construct low-tortuosity, mechanically robust 3D thick electrodes. LiFe 0.7 Mn 0.3 PO 4 nanoplates (LFMP NPs) and graphene are aligned along the growth direction of ice crystals during freezing and assembled into sandwich frameworks with vertical channels, which prompts fast ion transfer within the entire electrode and reveals a 2.5-fold increase in ion transfer performance as opposed to that of random structured electrodes. In the sandwich framework, LFMP NPs are entrapped in the graphene wall in a "plate-on-sheet" contact mode, which avoids the detachment of NPs during cycling and also constitutes electron transfer highways for the thick electrode. Such vertical-channel sandwich electrodes with mass loading of 21.2 mg cm −2 exhibit a superior rate capability (0.2C-20C) and ultralong cycle life (1000 cycles). Even under an ultrahigh mass loading of 72 mg cm −2 , the electrode still delivers an areal capacity up to 9.4 mAh cm −2 , ≈2.4 times higher than that of conventional electrodes. This study provides a novel strategy for designing thick electrodes toward high performance batteries.

Freeze Casting: From Low‐Dimensional Building Blocks to Aligned Porous Structures—A Review of Novel Materials, Methods, and Applications

“…Such hybrid structures, which tend to comprise a highly conductive cellular phase with an inserted secondary phase are attractive in energy materials, where a balance of electronic and mass transport is often of great importance. [ 29c,36c,69 ] The unique structure of graphene aerogels is key to achieving new levels of performance in such composites and represents a promising avenue of research towards further design and development of functional materials as discussed further in Section 4 of this work.…”

“…Toward thick electrodes with high active material loadings and improved volumetric energy density, aligned porous structured electrodes can provide effective ionic transport channels relative to traditional densely packed or random porous structures. [ 69,121 ] In freeze cast electrodes high levels of porosity further relieve the strain induced by volume changes during charge/discharge cycles. [ 32b,121e,122 ] Freeze cast scaffolds are also promising as fillers for solid polymer electrolytes, which can significantly improve the mechanical properties and maximize ionic conductivity.…”

“…In the field of Li‐ion batteries (LIBs), a coassembly freeze‐casting method was employed to construct low‐tortuosity and mechanically robust electrodes. [ 69 ] Vertically aligned LiFe 0.7 Mn 0.3 PO 4 nanoplates (LFMP NPs) and graphene hybrid frameworks, driving a 2.5‐fold increase in ion transfer and improved cycling performance rather than that of random structured electrodes ( Figure A). In the sandwich framework, LFMP NPs are entrapped in the graphene wall in a “plate‐on‐sheet” contact mode, which prevents the detachment of NPs during cycling and forms electron transfer pathways in the electrode.…”

“…Reproduced with permission. [ 69 ] Copyright 2019, Wiley‐VCH. B) Schematic diagram of the NS electrode and the catholyte within.…”

Thick Electrode Batteries: Principles, Opportunities, and Challenges

“…Other structural design approaches that utilize structural templates with aligned pores, such as natural wood and ice crystals, have also been reported and demonstrate high potential in constructing low‐tortuosity thick electrodes with high energy density and good structural stability and durability. Although increased energy density can be achieved through these pore engineering strategies in thick electrode design, the scalability of the fabrication process is generally limited, and therefore remains as a major challenge for the practical application of these approaches.…”