Layer-by-layer printing of multi-layered heterostructures using Li4Ti5O12 and Si for high power Li-ion storage

Sang Ho Lee,Chun Huang,Patrick S Grant

doi:10.1016/j.nanoen.2019.04.044

Abstract

Heterogeneous, multi-layered electrodes based on high power Li4Ti5O12 interleaved with a smaller fraction of high capacity Si were fabricated using layer-by-layer spray printing, with the goal of achieving a balance of power and capacity for Li-ion storage technologies. The faradaic charge/discharge behavior of the multi-layered hybrid electrodes was investigated as a function of (i) the thickness of the discrete Si layer within the multi-layered electrode, and (ii) the location of the Si layer within the electrode: on the top of the Li4Ti5O12 (closest to the separator), between two layers of Li4Ti5O12 (sandwich configuration) or at the Li4Ti5O12 base (next to the current collector but furthest from the separator). The optimum arrangement of Si spray printed on Li4Ti5O12 offered outstanding electrochemical performance at high current densities of 4000 mA/g and after 500 cycles when in a full Li-ion battery configuration coupled with a spray printed LiFePO4 cathode. The optimized multi-layered electrode was reliably reproduced as a double-sided coating over large area current collectors (≥20 cm × 15 cm). Sprayed printed electrodes were also readily patterned in-plane as well as through-thickness, offering the prospect for selective additions of high capacity Si or other active or inactive electrode components at specific locations to provide new Li-ion battery performance characteristics.

Highlights

Driven by increasing demand for wireless power sources for applications in portable electrics, home appliances, medicine and defence, there are continuing improvements in Li-ion battery (LIB) technology in terms of capacity, power density, fast charge, low weight and safety
The current collector was fixed on a heated vacuum chuck that was set to a temperature higher than the boiling point of both the isopropyl alcohol (IPA) and DI water (> 120 °C) allowing the effective in-situ drying of each thin layer of deposited suspension droplets and the successive superimposition of electrode layers over the pre-formed structure without any liquid buildup and re-suspension of pre-deposited materials
A LTO layer was first deposited on the current collector, and a Si layer was immediately deposited on LTO layer

Summary

Introduction

Driven by increasing demand for wireless power sources for applications in portable electrics, home appliances, medicine and defence, there are continuing improvements in Li-ion battery (LIB) technology in terms of capacity, power density, fast charge, low weight and safety. Its relatively poor electrical conductivity (∼10−13 S/cm) and ionic conductivity (∼10−12 cm2/s) inhibits its attractiveness for practical implementation To overcome these limitations, many attempts have been made to increase the specific capacity and intrinsic conductivity of LTO type materials e.g. doping with high energy density elements such as Si, Sn, SnO2, etc, [23,24,25] and the use of surface coatings such as conductive, ion-permeable carbon [26,27]. If electrodes are made of only LTO, excellent power performance may be realized at fast charge/discharge rates (> 10 C), but only with a relatively low capacity (∼175 mAh/g). The scalability of the through-thickness multilayered electrode and the possibility for in-plane patterning are investigated

Results and discussion

Conclusions

Spray printing process

Electrochemical tests