Enabling Aqueous Processing of Ni‐Rich Layered Oxide Cathode Materials by Addition of Lithium Sulfate

Abstract

Aqueous processing of Ni‐rich layered oxide cathode materials is a promising approach to simultaneously decrease electrode manufacturing costs, while bringing environmental benefits by substituting the state‐of‐the‐art (often toxic and costly) organic processing solvents. However, an aqueous environment remains challenging due to the high reactivity of Ni‐rich layered oxides towards moisture, leading to lithium leaching and Al current collector corrosion because of the resulting high pH value of the aqueous electrode paste. Herein, a facile method was developed to enable aqueous processing of LiNi0.8Co0.1Mn0.1O2 (NCM811) by the addition of lithium sulfate (Li2SO4) during electrode paste dispersion. The aqueously processed electrodes retained 80 % of their initial capacity after 400 cycles in NCM811||graphite full cells, while electrodes processed without the addition of Li2SO4 reached 80 % of their capacity after only 200 cycles. Furthermore, with regard to electrochemical performance, aqueously processed electrodes using carbon‐coated Al current collector outperformed reference electrodes based on state‐of‐the‐art production processes involving N‐methyl‐2‐pyrrolidone as processing solvent and fluorinated binders. The positive impact on cycle life by the addition of Li2SO4 stemmed from a formed sulfate coating as well as different surface species, protecting the NCM811 surface against degradation. Results reported herein open a new avenue for the processing of Ni‐rich NCM electrodes using more sustainable aqueous routes.

Carrageenans as Sustainable Water-Processable Binders for High-Voltage NMC811 Cathodes

“… 29 In addition, the larger number of sulfonate groups present in the 3SO 3 – Carr binder may contribute to the protection of the NMC811 particles against water, achieving a more stable cycling than the 1SO 3 – Carr and 2SO 3 – Carr . This effect could be similar to the one observed by Heidbüchel et al 30 that have recently reported the positive impact of the addition of Li 2 SO 4 during the aqueous processing of NMC811 cathodes since a protective coating around the active material was observed by XPS measurements.…”

Influence of Phosphate Surface Coating on Performance of Aqueous‐Processed NMC811 Cathodes in 3 Ah Lithium‐Ion Cells

“…It is likely that phosphate surface species were also present in that case. Several other groups achieved higher initial DCs of up to 190 mAh/g CAM [18,27,44,45] . However, a lower ratio of anode:cathode capacity (N/P) was used within these studies, i. e., between 1.2 : 1 and 1.15 : 1.…”

“…Several other groups achieved higher initial DCs of up to 190 mAh/g CAM . [18,27,44,45] However, a lower ratio of anode: cathode capacity (N/P) was used within these studies, i. e., between 1.2 : 1 and 1.15 : 1. The N/P ratio of the cells in this study was 1.35 : 1.…”

“…These strategies including the addition of acids, [16][17][18][19][20][21] the use of pressurized CO 2 , [22] adjusting the binder composition, [3,14,21,23] employing carbon-coated aluminum foil [24] and applying surface coatings. [13,[25][26][27] The latter approach is intended to limit the contact between the active material surface and water, ultimately reducing lithium leaching and enhancing cycling performance. To demonstrate the impact of the chosen strategy, most studies only carry out lab-scale tests using comparably small cells of < 100 mAh.…”

“…To mitigate these problems, several strategies have been reported in literature. These strategies including the addition of acids, [16–21] the use of pressurized CO 2 , [22] adjusting the binder composition, [3,14,21,23] employing carbon‐coated aluminum foil [24] and applying surface coatings [13,25–27] . The latter approach is intended to limit the contact between the active material surface and water, ultimately reducing lithium leaching and enhancing cycling performance.…”