Applying Established Water-Based Binders to Aqueous Processing of LiNi_0.83Co_0.12Mn_0.05O₂ Positive Electrodes

Abstract

The combination of two different binders: styrene-butadiene rubber (SBR) and polyacrylic acid (PAA), in combination with carboxymethylcellulose (CMC) has been investigated for aqueous electrode preparation of LiNi0.83Co0.12Mn0.05O2 positive electrodes. The use of Ni-rich active materials in Li-ion batteries is becoming industry standard, however, such Ni-rich cathode materials are sensitive to water, which makes the aqueous electrode manufacturing especially challenging and based on industry-information even impossible. The preparation of aqueous Ni-rich electrodes with areal capacities of 2.7 mAh cm−2 and densities of up to 3.5 g cm−3 was investigated and optimized. The electrochemical evaluation in bi-layer pouch cells showed that the performance depends heavily on the individual combination of binders. Using PAA binders, the best electrode reached 80% capacity retention only after 470 cycles. In contrast, the best electrode with SBR binder performed very similar to the PVdF reference electrode in view of rate capability and a specific 1 C capacity with 177 mAh gCAM −1 compared to 179 mAh gCAM −1 of the PVdF reference electrode. In addition, this SBR-based electrode showed excellent cycling stability at 1 C/1 C with capacity retention of 84% after 1,000 cycles; therefore, matching typical requirements for such electrodes in electric vehicle batteries.

From Materials to Cell: State-of-the-Art and Prospective Technologies for Lithium-Ion Battery Electrode Processing

“…At the academic level, CMC is possible to use by itself as a binder, as several studies use binder contents that are greater than what is seen industrially (≥5 wt %). When using only CMC in a more realistic amount (≤3.0 wt %), the electrode is rigid and unable to withstand the various steps in the roll-to-roll process . The CMC/SBR combination widely used in aqueous-processed graphite anodes has largely been ignored for cathodes due to the perception that SBR is unstable around 4.2 V vs Li/Li + ; however, a recent study has shown excellent cyclability of Ni-rich NMC cathodes with realistic conditions (2.6 mAh/cm 2 , 93 wt % NMC) using CMC and SBR as binder .…”

“…When using only CMC in a more realistic amount (≤3.0 wt %), the electrode is rigid and unable to withstand the various steps in the roll-to-roll process . The CMC/SBR combination widely used in aqueous-processed graphite anodes has largely been ignored for cathodes due to the perception that SBR is unstable around 4.2 V vs Li/Li + ; however, a recent study has shown excellent cyclability of Ni-rich NMC cathodes with realistic conditions (2.6 mAh/cm 2 , 93 wt % NMC) using CMC and SBR as binder . Polyacrylic acid (PAA) and its lithium-substituted variant have also been shown to be good binders due to hydrogen-bonding between the two carboxylic groups causing cross-linking in the former and lithium-ion-conduction ability and excellent electrochemical stability in the latter. ,− CMC, PAA, and poly­(ethylene oxide) have been combined to create a binder suitable for thick aqueous-processed cathodes, which are desirable in energy-dense applications, as discussed in section .…”

Biobased Acrylic Latexes/Sodium Carboxymethyl Cellulose Aqueous Binders for Lithium-Ion NMC 811 Cathodes

“…The equivalent circuit used to fit the EIS results is presented on the top of Figure 5 and is composed of an electrolyte resistance (R e ), a contact resistance (R contact ) between the current collector and the electrodes, and a charge transfer resistance (R ct ) for the intercalation−deintercalation of lithium ions in the electrodes. 30 The two latter processes are represented by double layer capacitance (CPE constant and CPE ct , respectively). The most relevant data of the fitted Nyquist plots are presented in Table S2.…”

Water-Based LiNi0.83Co0.12Mn0.05O2 Electrodes with Excellent Cycling Stability Fabricated Using Unconventional Binders

“…The electrode with polyacrylic acid (PAA, M W = 450000, Sigma Aldrich) was prepared as described in our previous work. 57 The detailed preparation procedure can be found there. The binder ratio in this electrode between PAA and CMC was 1.5%.…”

“…The details of the graphite-based negative electrode with an areal capacity of 2.9 mA h cm −2 and density of 1.5 g cm −3 are described elsewhere. 57 Electrode characterization.-For the Z-direction tensile strength measurements, a ZwickRoell Z2.5 device was used. On top of the two compression plates a double-sided adhesive tape (3 M) was fixed and then the electrode was pressed on one of them.…”