Performance Comparison of LMNO Cathodes Produced with Pullulan or PEDOT:PSS Water-Processable Binders

Abstract

The aim of this paper is to demonstrate lithium metal battery cells assembled with high potential cathodes produced by sustainable processes. Specifically, LiNi0.5Mn1.5O4 (LMNO) electrodes were fabricated using two different water-processable binders: pullulan (PU) or the bifunctional electronically conductive poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS). The cell performance was evaluated by voltammetric and galvanostatic charge/discharge cycles at different C-rates with 1M LiPF6 in 1:1 (v:v) ethylene carbonate (EC):dimethyl carbonate (DMC) (LP30) electrolyte and compared to that of cells assembled with LMNO featuring poly(vinylidene difluoride) (PVdF). At C/10, the specific capacity of LMNO-PEDOT:PSS and LMNO-PU were, respectively, 130 mAh g−1 and 127 mAh g−1, slightly higher than that of LMNO-PVdF (124 mAh g−1). While the capacity retention at higher C-rates and under repeated cycling of LMNO-PU and LMNO-PVdF electrodes was similar, LMNO-PEDOT:PSS featured superior performance. Indeed, lithium metal cells assembled with PEDOT:PSS featured a capacity retention of 100% over 200 cycles carried out at C/1 and with a high cut-off voltage of 5 V. Overall, this work demonstrates that both the water-processable binders are a valuable alternative to PVdF. In addition, the use of PEDOT:PSS significantly improves the cycle life of the cell, even when high-voltage cathodes are used, therefore demonstrating the feasibility of the production of a green lithium metal battery that can exhibit a specific energy of 400 Wh kg−1, evaluated at the electrode material level. Our work further demonstrates the importance of the use of functional binders in electrode manufacturing.

Electronic properties of lithium-ion battery cathodes studied in ion-gated transistor configuration

“…In our previous studies, 27 , 28 we demonstrated that the lithiation/delithitation processes are highly reversible for both NMC532 and LNMO-bulk electrodes. These electrodes can be charged/discharged over hundreds of cycles without significant structural, morphological, or compositional changes, when operated in LP30 electrolyte.…”

“…These reversible peaks can be assigned to the Mn 4+ /Mn 3+ , Ni 3+ /Ni 2+ , and Ni 4+ /Ni 3+ redox couples, respectively. 28

Figure 1 Cyclic voltammograms of bulk (A) NMC532- and (B) LNMO-based electrodes in the electrolyte LP30, in a Swagelok-like cell including a metallic lithium disk serving both counter and reference electrode. Potential scan rate 50 μV s -1 .

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“…32-0581), expected for LiNi 0.5 Mn 1.5 O 4 . 28 SEM images ( Figure S4 ) indicates that LNMO particles are well dispersed in the carbon-binder matrix and the composite layer is homogenously distributed on the substrate.…”

“…Finally, the electrodes were transferred and stored in a dry Ar box (MBraun, H 2 O, and O 2 <1 ppm). 27 , 28 …”

The ENEA′s 2019–2021 Three‐Year Research Project on Electrochemical Energy Storage

“…Specifically with PEDOT:PSS a greater utilization of the active material was achieved compared to a similar PVdF‐based electrode (Figure 2). [35] …”