Experimental Visualization of Commercial Lithium Ion Battery Cathodes: Distinguishing Between the Microstructure Components Using Atomic Force Microscopy

Abstract

The integration of lithium-ion batteries (LIB) into transportation through the implementation of hybrid and electric vehicles is driving fundamental research into improving their performance and lifetime. The rapid production of new electric vehicles by several popular brands also raises the question of how much material will eventually need to be reused or recycled. With a combination of an enhanced fundamental analysis of commercially utilized electrodes with fundamental chemical knowledge, answers to the scientific material challenges of lithium ion batteries will aid in not only the implementation of battery powered electrical transport but also the development of end of life recycling processes. Here, using quantitative nanomechanical and conductive atomic force microscopy, which are nondestructive and rapid techniques, the different components of the composite electrode are unveiled at the nanoscale, identifying the mechanism by which the active material binds together and how the conductive network is formed. Changes in the polymer binder network are observed in an aged cell and are shown to affect the mechanical integrity of the electrode structure, which can lead to the failure of the electrode. The links between nanomechanical and macro-mechanical properties were evaluated using a scratch test and optical microscopy to show that the mechanical integrity of the aged cell was weaker than that of the untouched cell.

The importance of design in lithium ion battery recycling – a critical review

“…Studies by Demirocak et al revealed that mechanical degradation is due to a reduced crystallinity of PVDF, as indicated by a decreasing hardness and modulus of elasticity with age. 60,61 This can affect the electrode by reducing the adhesiveness of the binder to the active material and current collector (i.e. loss of contact).…”

Gelatin and Alginate Binders for Simplified Battery Recycling

“…Here, the AFM scan produces modulus data through the probe coming into contact with the surface until a set point is reached, generating a force–time curve for every pixel on the image. Terreblanche et al used this technique to identify the different electrode components for NMC cathodes, and the same technique and modulus models were used in this study . It should be noted that the modulus images show a semiquantitative, comparative contrast in the modulus values; quantitative values for the modulus could not be acquired for these samples.…”

“…In this mode, the probe comes into contact with the surface until a specified force set point is reached, generating a force versus time curve for every pixel of the image allowing modulus values to be generated from these curves. This allows for the identification of the different electrode components on the surface, as done previously for NMC by Terreblanche et al 36 A RTSEP-300 probe with a spring constant of 40 N/m was used to acquire the height images and data used by the Nanoscope 16.4 software to calculate the Sneddon Modulus, giving a modulus scan of the surface. Scratch testing was carried out using a ST200 scratch tester with a diamond probe.…”

Selective bacterial separation of critical metals: a sustainable method for recycling lithium ion batteries

“…To investigate metal removal/precipitation from vehicular battery leachates, two commercial LIB cathodes (Nissan Leaf) were leached with two different mineral acids, H2SO4 or HCl, both widely used in hydrometallurgy. 18 These cathode materials contained either Li, Ni, Mn and Co in a ratio of 50% nickel, 30% manganese, and 20% cobalt (NMC-532), or a mixture of approximately 70% lithium manganese oxide spinel (LMO) with 25% lithium nickel manganese cobalt oxide 19 , referred to hereafter as A1C and B1C, respectively. The concentration of metals (Al, Co, Mn, Li and Ni) in these LIB leachates was dependent upon the origin of the cathode material, solvent used and leaching temperature (ESI, Table S1).…”