Zinc-Doped High-Nickel, Low-Cobalt Layered Oxide Cathodes for High-Energy-Density Lithium-Ion Batteries

Abstract

High-Ni layered oxides with Ni contents greater than 90% are promising cathode candidates for high-energydensity Li-ion batteries. However, drastic electrode−electrolyte reactions and mechanical degradation issues limit their cycle life and practical viability. We demonstrate here that Li-Ni 0.94 Co 0.04 Zn 0.02 O 1.99 (NCZ), obtained by incorporating 2 mol % Zn 2+ into an ultrahigh-Ni baseline cathode material LiNi 0.94 Co 0.06 O 2 (NC), delivers superior cell performance. NCZ retains 74% of the initial capacity after 500 cycles in a full cell assembled with a graphite anode, outperforming NC (62% retention). NCZ also possesses a higher average discharge voltage relative to NC with an outstanding average voltage retention of over 99% after 130 cycles in half cells. Bulk structural investigations unveil that Zn doping promotes a smoother phase transition, suppresses anisotropic lattice distortion, and maintains the mechanical integrity of cathode particles. Furthermore, NCZ shows an enhanced interphase stability after long-term cycling, in contrast to the seriously degraded surface chemistry in NC. This work provides a practically viable approach for designing higher-energy-density high-Ni layered oxide cathodes for lithium-ion batteries.

In‐Depth Analysis of the Degradation Mechanisms of High‐Nickel, Low/No‐Cobalt Layered Oxide Cathodes for Lithium‐Ion Batteries

“…Figure 4b captures the depth profiles of several secondary-ion fragments of interest on the surface of the high-Ni cathode materials up to a sputter depth of 100 nm. The PO 2 and PO 3 fragments correspond to the reaction products of PF 6 anion with nucleophilic oxygen atoms from intermediate organic solvent decomposition species; [38,39] LiO 2 and LiF 2 fragments represent Li 2 O and LiF precipitates from electrolyte decomposition reactions; NiF 3 fragment is a marker for the dissolution product of HF corrosion on the cathode surface before dissolving into the electrolyte and diffusing onto the anode surface (transition metal dissolution); C 2 HOfragment derives from the alkyl carbonate species that follow the decomposition of carbonate solvents; 62 Nifragment represents the bulk cathode structure. The colored scale bar at the top demonstrates the CEI thickness on the cathode surface.…”

“…This suggests that other degradation mechanisms, such as active material isolation due to particle cracking and surface reconstruction, are likely responsible for the deterioration of its layer (yellow) and a C 2 HOinner organic layer (green) over the bulk of the cathode materials (represented by 62 Niin purple).…”

Unveiling the Stabilities of Nickel‐Based Layered Oxide Cathodes at an Identical Degree of Delithiation in Lithium‐Based Batteries

“…[ 16–21 ] Consequently, Ni content is widely assumed to primarily account for the instability of high‐Ni NMC cathodes. Many different pathways, such as elemental doping and surface modulation by thin layer, [ 12,23–26 ] have been used to improve the stability of high‐Ni NMC. Among these pathways, inert elemental doping (Mg, Al, Zr, Ti, etc.)…”

Positron Annihilation Spectroscopy as a Diagnostic Tool for the Study of LiCoO2 Cathode of Lithium-Ion Batteries

“…The development of novel and high-performing materials in this technology is an urgent need. In this regard, the research is primarily focused on: (i) the transition from the costly and capacity limited graphite anode towards silicon and lithium metal [2][3][4][5][6], (ii) the designing of solid-state ceramic and polymer electrolytes endowed with a wide electrochemical stability window and stable towards the Li-metal anode [7][8][9][10][11][12][13][14][15][16], and (iii) the development of high-voltage and high-energy cathode materials [17][18][19][20][21][22][23]. This latter component (i.e., the cathode) typically limits the energy density of the resulting full cell, thus becoming one of the most important materials to focus attention on.…”