Real-time observations of lithium battery reactions—operando neutron diffraction analysis during practical operation

Abstract

Among the energy storage devices for applications in electric vehicles and stationary uses, lithium batteries typically deliver high performance. However, there is still a missing link between the engineering developments for large-scale batteries and the fundamental science of each battery component. Elucidating reaction mechanisms under practical operation is crucial for future battery technology. Here, we report an operando diffraction technique that uses high-intensity neutrons to detect reactions in non-equilibrium states driven by high-current operation in commercial 18650 cells. The experimental system comprising a time-of-flight diffractometer with automated Rietveld analysis was developed to collect and analyse diffraction data produced by sequential charge and discharge processes. Furthermore, observations under high current drain revealed inhomogeneous reactions, a structural relaxation after discharge, and a shift in the lithium concentration ranges with cycling in the electrode matrix. The technique provides valuable information required for the development of advanced batteries.

Understanding Rechargeable Battery Function Using In Operando Neutron Powder Diffraction

“…Custom‐designed cell types for in operando NPD measurements can be summarized as the flat‐plate design with a single electrode/separator/electrode layer, the prismatic design with several stacked layers,4b,16a–c,e,45,49,61a,b,d,e the cylindrical type containing rolled layers,8,16d,23,25,29,43,50,51,56,58,61c,62,64 and the confined electrode type where the beam predominantly illustrates the electrode of interest ( Figure ).…”

“…Cylindrical Rolled Layer Cell : The cylindrical rolled layer cell contains an electrode and separator roll inserted into a cylindrical can, such as in the commercial 18650 cell, where the relatively large amount of active materials yields intense data despite the hydrogen in the electrolyte and separators . Custom cells have been made using cans composed of aluminum, quartz, nickel‐plated steel,62a and vanadium 61c,62b–e.…”

Dependency of the Charge–Discharge Rate on Lithium Reaction Distributions for a Commercial Lithium Coin Cell Visualized by Compton Scattering Imaging

“…Moreover, people expect fast-charging batteries at a similar refueling speed as in the gasoline car. However, in a previous neutron diffraction study, it was reported that inhomogeneous reactions occur in the graphite-negative electrode at a high-speed charge-discharge rate [1]. These inhomogeneous reactions are related to the degradation of the battery performance; furthermore, they carry some great risks.…”

“…Moreover, a line-shape of the Compton scattered energy spectrum, called the Compton profile, is obtained from this incoherent scattering technique and depends on the element. Here, the Compton profile, J(p z ), is shown in the following equation [6], J(p z ) = ρ(p)dp x dp y (1) where ρ(p) is the electron momentum density, p = (p x , p y , p z ) is the momentum, and p z is assumed to lie along the direction of the scattering vector. The ρ(p) is expressed by the following [7,8],…”

Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex II: Neutron Scattering Instruments

“…The full-scale usage of SPICA has just begun. The first battery study on the structure dependence of the charge-discharge rate was published in 2016 [84]. SPICA will be used to carry out experiments on material science and observe structural changes in practical devices under an operative condition.…”