Quantifying Mass Transport during Polarization in a Li Ion Battery Electrolyte by in Situ ⁷Li NMR Imaging

Abstract

Poor mass transport in the electrolyte of Li ion batteries causes large performance losses in high-power applications such as vehicles, and the determination of transport properties under or near operating conditions is therefore important. We demonstrate that in situ (7)Li NMR imaging in a battery electrolyte can directly capture the concentration gradients that arise when current is applied. From these, the salt diffusivity and Li(+) transport number are obtained within an electrochemical transport model. Because of the temporal, spatial, and chemical resolution it can provide, NMR imaging will be a versatile tool for evaluating electrochemical systems and methods.

Constant-time chemical-shift selective imaging

“…The NMR cell used in these experiments is similar to that described previously [13,14]. The axially symmetric cell contains two cylindrical and thin (ca 100 lm) lithium metal plates at its opposite ends that are connected by wires to an external current/ voltage source.…”

“…The salt is dissociated and therefore the lithium exists in the electrolyte as Li + . The purpose of this experimental arrangement is to be able to measure in situ the mass transport of Li + as affected by current applied to the cell [14].…”

In situ methods for Li-ion battery research: A review of recent developments

“…NMR is a quantitative method, but it yet remains challenging to obtain spatially resolved measurements. Recently, however, several in situ NMR studies have been conducted, measuring Li-ion concentration gradients [80,81] and monitoring lithium dendrite formation [82]. Klett et al [80] employed a 10 mm cylindrical cell to study the concentration gradient build up in LiPF 6 electrolyte under current flowing conditions.…”

In situ transmission electron microscopy and spectroscopy studies of rechargeable batteries under dynamic operating conditions: A retrospective and perspective view

“…Due to the possibility of directly monitoring dynamic processes, in situ methods based on spectroscopies, 35,42,43,45,46 atomic force microscopy (AFM), 43,49 and SEM imaging 50,51 have provided useful information regarding the structural evolution of the electrode materials during a battery's operation. 49,[52][53][54][55][56][57][58][59][60] Because of the TEM's high-vacuum operation and the vacuum incompatibility of liquid electrolyte used for most rechargeable batteries, including the Li-ion battery, the fundamental challenge is the integration of the liquid electrolyte and electrode system in the TEM's highvacuum column.…”