Cycling Performance and Limitations of LiNiO₂ in Solid-State Batteries

Abstract

Solid-state batteries (SSBs) have been touted as the next major milestone for electrochemical energy storage, improving safety and enabling higher energy densities. LiNiO 2 (LNO) has long been considered a promising cathode material; however, its commercial implementation is complicated by stability issues, including reactivity toward the electrolyte components. To address this, a detailed study probing the electrochemical behavior of LNO in pellet-stack SSB cells, in combination with argyrodite Li 6 PS 5 Cl solid electrolyte (SE) and Li 4 Ti 5 O 12 anode, is for the first time presented herein. In this configuration, LNO delivers a specific capacity of 105 mAh/g LNO after 60 cycles (0.2C, 45 °C), which was improved considerably to 153 mAh/g LNO by applying a LiNbO 3 coating to the material. Using complementary operando and ex situ characterization techniques, contributions to the initial capacity loss and capacity fading could be resolved and attributed to decomposition of the argyrodite SE and to volume changes and gas evolution in LNO.

Cycle Degradation Analysis by High Precision Coulometry for Sulfide-Based All-Solid-State Battery Cathode under Various Potentials

“…These changes in the ED profiles of argyrodite-structured SE indicate that the SE exhaled the products, such as LiCl and Li2S, and decomposed into an amorphous phase. These results are similar to those previously reported, 2,12 and it is significant that the HPC parameters further support them in this study. Conversely, when looking at the active material of NCM523, a significant change in particle size was observed in the TEM image at the highest potential of 4.65 V vs. Li/Li + .…”

“…2 However, the decomposition reactions gradually proceed at the interface of sulfide SE/NCM in conditions such as a high temperature environment, high cathode potential, and after a long-term charge/discharge cycle testing. 2,11,12 Elucidating the not-fully-understood decomposition side reactions in more detail will be an important finding for further material development and improvement of battery performance of ASSBs using sulfide SE in the future.…”

Advanced Nanoparticle Coatings for Stabilizing Layered Ni‐Rich Oxide Cathodes in Solid‐State Batteries

“…This suggests that (chemo‐)mechanical degradation within the cathode does not play a critical role in the differences in cyclability between the bare and coated NCM85 CAMs in these cells. [ 8 ] Additionally, XRD data collected from the cathode composites in the pristine state and after cycling showed that the bulk structure of Li 6 PS 5 Cl remains stable (see Figure S22 and Table S4, Supporting Information).…”

“…While the pronounced doublet at 161.7/162.9 eV is characteristic of the PS 4 3− units of the argyrodite structure, that at a lower binding energy (160.3/161.4 eV) represents Li 2 S impurities (or “free” S 2− ions). [ 8,18,45 ] The other two minor doublets located at higher binding energies (162.9/164.1 and 163.7/164.9 eV) can be assigned to various compounds, including anionic frameworks that thiophosphate phases can pass through upon oxidative decomposition toward the formation of P 2 S 5 (e.g., P 2 S 7 4− , P 2 S 6 2− ) and “S 0 ” species, such as long‐chain polysulfides. [ 8,18 ] The P 2p spectrum showed two doublets at 132.0/132.8 and 133.0/133.9 eV, representing the PS 4 3− units and the aforementioned degradation products and/or lithium phosphate, respectively.…”

“…[ 1,3,4,6 ] In addition, SSBs have other advantages, such as a wider operation temperature range or no cross‐talk effects due to electrode dissolution. [ 7,8 ]…”