## 3 Introduction  
The full field transmission Soft X-ray microscopy (TXM) available at ALBA's MISTRAL Beamline provides unique access to the chemical state, nanoscale spatial distribution, of light elements-containing materials. The practically accessible energy range (390-800 eV) permits to access among others, the O K-edge and the L-edges of several transition metals (TMs). The reported 2D X-ray imaging of electrochemically discharged Li- and Na/Obattery cathodes probing the oxygen chemical state of the involved reaction products by a full XANES spectrum per pixel is a good example of the TXM capabilities [1; 2; 3; 4; 5].  
Moreover, intensive investigation in the past few years has demonstrated that oxygen also has remarkable redox activity in many battery intercalation compounds [6; 7; 8; 9; 10; 11; 12], involving the production of trapped oxygen [13; 14] and simultaneous TM migration to the lithium layer [15; 16]. Oxygen is formally the anion in the host material and its oxidation is often referred to as anion redox, in contrast to the more established and understood redox chemistry of the TM cations. This supplemental activity from the anion provides additional capacity to cathode material, and therefore larger energy density, which explains the strong interest for these phenomena, beyond the fundamental point of view. The most studied group of this class of electrode active materials is the lithium-rich and cobalt poor nickel, manganese, cobalt oxide, with general formula Li[Li\({}_{0.2}\)M\({}_{0.8}\)]O\({}_{2}\), where M represents one or a few TMs.  
The presence and the distribution of higher valence oxygen in the active material is of critical relevance for a full understanding of the redox process in this system, and finally guides the design of more stable and effective materials. This could not be unquestionably achieved by diffraction techniques, while most X-ray Absorption Spectroscopy (XAS) beamlines use hard X-rays and are highly effective for TMs but cannot directly access oxygen. We have performed a combined hard and soft X-ray absorption study on uncoated and VOx-coated Li[Li\({}_{0.2}\)Ni\({}_{0.16}\)Mn\({}_{0.56}\)Co\({}_{0.08}\)]O\({}_{2}\) electrode materials at different states of charge. This has allowed us to find evidence of an unexpected Mn reduction during charge with the formation of high- and low-spin Mn(III) that is partially reverted to Mn(IV) during discharge [17]. Quantification of the spinel environment formation and the average oxygen stoichiometry and oxidation state during charge-discharge has been also provided [18]. In these studies, TXM across the O K and Mn L\({}_{3}\) edges provided bulk information on the different chemical species distributions on a particular Li[Li\({}_{0.2}\)M\({}_{0.8}\)]O\({}_{2}\) cathode at the nanometer scale (40 nm of space resolution) by focusing over isolated nanoparticles of around 100-300 nm size. Herein, we present a focus on soft X-ray imaging, showing in detail novel analysis approaches for improving quantification and representation of large set of data represented by energy-dependent TXM images. This adds to the techniques we already presented previously with application to alkali-oxygen cathodes [1]. In particular, here we propose a data correction to extend the absorbance linearity range, and a phase map representation, a tool to precisely isolate pixels and regions of the sample with different spectral shape, where target spectral features are enhanced/suppressed. From them, 2D maps of different chemical environments or phases are obtained, which helps to visualize the electrode material and analyze its homogeneity.