Combination of 3D current collectors and in situ polymerized electrolytes enabling high-mass-loading cathodes for solid-state lithium batteries

Abstract

Solid-state lithium batteries (SSLBs) are promising energy storage devices in the future due to their high theoretical energy density and enhanced safety. However, the practical energy density of SSLBs is severely constrained by the limited mass loading of cathode materials, which is related to sluggish charge transfer inside the thick cathodes. In this work, the solid-state batteries with high-mass-loading cathodes are realized by introduction of three-dimensional (3D) electronic-conductivity current collectors and in situ solidification of polymer electrolytes. The porous electronic current collectors of 3D carbon felts accommodate the flowing cathode slurry with considerably increased loading of cathode materials. Subsequently, the in situ solidified polymer electrolytes ensure conformal ionic conducting channels inside the cathodes, along with the formation of intimate and flexible contacts at cathode/electrolyte interfaces. In this way, the solid-state LiFePO4/garnet/Li batteries with cathode loading of 6.2 mg cm−2 show an initial discharge capacity of 159.4 mAh g−1 and a capacity retention of 92.1% after 100 cycles at 30 °C and 0.1 C. Furthermore, the cathode mass loading as high as 27.8 mg cm−2 is achieved with a corresponding areal capacity of approximately 4.2 mAh cm−2. This work proposes a promising unique cathode architecture for solid-state lithium batteries with high mass loading of the cathode.

Developments, Novel Concepts, and Challenges of Current Collectors: From Conventional Lithium Batteries to All‐Solid‐State Batteries

“…Carbonaceous materials are also favoured as current collectors in lithium batteries which have been extensively studied. The carbon‐based current collectors are featured with many pivotal advantages, including mechanical integrity to accommodate the volume change, superior ionic conductivity, large available surface area, and rich functionalization chemistries to increase the affinity to Li metal or active materials [34,57–60] . Li et al [60] .…”

“…It is proven that the nucleation of Li on the current collector in anode‐free lithium metal batteries is significantly improved if an initial chemical pre‐lithiation of the current collector surface is performed (Figure 4 c). [58] On the surface of the pre‐lithiated copper substrate, the grain boundaries have been filled with lithium which hinders further diffusion of lithium into the copper during the early stages of the lithium nucleation (and growth), thus, a greater number of lithium nucleation with a more homogeneous distribution are obtained which further facilitates 2D nucleation and growth [70] . Although the application of alloy‐based current collectors is beneficial to greatly improve the energy density of LIBs, the instability of alloy network which result in strong diffusion dependence of Li mobility on the composition of alloys, and alloy material degradation arising from large volumetric and structural changes during cycle obstacles their currently utilization [71] …”