Preparation, formulation and deposition of mica flake supported cobalt oxide for nanostructured lithium ion battery anodes

Electrophoretic Deposition of Out‐of‐Plane Oriented Active Material for Lithium‐Ion Batteries

“…[ 32 ] A popular solution, also applied in our earlier work using Co 3 O 4 –mica flakes is the inclusion of carbon black as a conductive additive. [ 44 ] In the present work, carbon black could not be deposited simultaneously with or after Co 3 O 4 –mica flake deposition without disrupting the out‐of‐plane morphology. Therefore, we first deposited a layer of carbon black by EPD before carrying out Co 3 O 4 –mica flake deposition according to the standard procedure (see the Experimental Section).…”

“…[ 42,43 ] Recently, we reported a wet chemical oxidation route for the coating of commercially available rutile/mica flakes with nanostructured Co 3 O 4 and demonstrated that lithium‐ion battery anodes based on such hybrid particles were electrochemically viable, had good cycling stability and a reasonable specific capacity of ≈650 mAh g −1 . [ 44 ] Nevertheless, we found that the simple electrode‐fabrication process based on casting or doctor‐blading of a slurry led to mainly flat‐lying flakes, a microstructure that is not expected to support efficient ion or electron transport. [ 5 ] Given the highly anisotropic shape of mica flakes, we considered whether it is possible to align the flakes in an out‐of‐plane arrangement during electrode fabrication.…”

“…The CV measurement of the anode comprising out‐of‐plane oriented Co 3 O 4 –mica flakes (Figure 3a) shows qualitatively similar behavior to electrodes produced with the same active material in previous work. [ 44 ] In particular, there are two cathodic (reduction) peaks and three anodic (oxidation) peaks. The latter were somewhat less sharp in our earlier work.…”

“…Moreover, the initial discharge capacity at C/10 of over 800 mAh g −1 is improved compared with our earlier work, where no special orientation of the flakes was achieved. [ 44 ] Nevertheless, a significant reduction in specific capacity over successive cycles at C/10 can be seen for the out‐of‐plane oriented electrode. This was not the case in our earlier study which included a binder.…”

“…Despite these excellent improvements, solely resulting from the change in electrode architecture, the cycle stability of the out‐of‐plane oriented electrode was inferior to that of an electrode produced in earlier work with randomly oriented flakes and an alginate binder. [ 44 ] Consequently, future work will seek to incorporate a suitable binder into the out‐of‐plane architecture and in particular to provide sufficient robustness of the critical interface between the flake base and the substrate. Moreover, to further improve the volumetric capacity, thinner flakes, e.g., omitting the rutile layer, will be used and strategies to pack the flakes more efficiently in the layer during EPD established.…”