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The dissolution of transition metals is the main reason for the capacity fading and structural degradation of Ni‐rich cathode materials. In this work, NiF2 is used as functional electrolyte additive for the first time to improve the performance of LiNi0.6Co0.2Mn0.2O2 cathodes by the chemical‐equilibrium principle. The suppression of transition‐metal dissolution, especially Ni, is proved by energy disperse spectroscopy and inductively coupled plasma analyses. The NiF2 additive can stabilize the cathode structure by relieving the dissolution of transition metals, which is confirmed by morphology and structure analyses. Moreover, the NiF2 additive also reduces side reactions of the cell, which is verified by self‐discharge tests and coulombic efficiency analysis. As a result, the addition of 100 ppm NiF2 elevates the capacity retention of the Li/NCM622 half‐cell from 69.53 to 79.67 % after 100 cycles, and the 100 ppm NiF2‐containing cathode delivers an initial capacity of 174.0 mAh g−1 even at 8 C after 50 cycles. [ABSTRACT FROM AUTHOR]

Cadmium oxides (CdO), an important semiconductor material, have many superior properties when used as a cathode material for nickel-cadmium batteries. Here, the coating and the doped co-modified LiNi 0.8 Co 0.15 Al 0.05 O 2 cathode are constructed by a continuous wet chemical process and a high-temperature sintering process, wherein the Cd2+ are uniformly doped in a gradient form and the CdO protective layer is distributed on the outer surface of secondary particles. The Cd-modified NCA material has more stable interfacial and crystal lattice structure, thereby inhibiting harmful phase transitions and side-reactions. Accordingly, the modified sample has excellent electrochemical performance and maintaining a complete spherical morphology during long cycling compared to the pristine sample. In addition, as a pillar ion, cadmium increases the plate spacing and lithium-ion diffusion kinetics. The electrochemical results show that the capacity retention of the modified sample Cd-2000 reached 96.5% and 90.6% after 100 cycles and 200 cycles respectively at 1 C. At the high current rate of 8 C, the initial capacity and retention (100 cycles, 3.0–4.3 V) reach 166.2 mAh g−1 and 95.2%, respectively. Besides, the results of electrochemical impedance spectroscopy (EIS) reveal that CdO modification could decrease the resistance of the cell polarization and impedance increment upon cycling. Image 1 • The Cd-modified NCA cathode is prepared by simple wet chemical precipitation-calcination techniques. • The modification of LiNi 0.8 Co 0.15 Al 0.05 O 2 cathode was achieved by the synergistic effect of CdO coating and Cd ion doping. • After modification, the interface and crystal structure stability is improved. • The Cd-modified cathode material achieves excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

The surface instability and the structure degradation in Ni-rich cathode materials have been considered to the primary issues causing the severe capacity fading. In this study, a viable and effective approach to fabricate the yttrium modified LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) cathode materials with higher electrochemical performance by solid-state method is reported. The yttrium modified materials exhibit a notably enhanced electrochemical performance, which delivers a discharge capacity of 169.8 mAh g−1 over 3.0–4.3 V at 1 C corresponding capacity retention of 95.3% after 200 cycles. Besides, the capacity of the modified materials at higher rate (8 C) increase to 156.9 mAh g−1. With a careful and in-depth investigation, we found that the improved electrochemical performance can be attributed to the Y doping, which provides a powerful Y-O bond in the transition metal layers and effectively improves the structure stability. Additionally, the Ni2+ existing in the Li slabs to some extent exert a positive effect on suppressing the further cation migration and stabilizing the lithium slabs. Based on our work, we believe the modification strategy has the potential application in the cathode materials. • A strategy of Y modification. • The enhanced structural stability. • The excellent cyclic performance. [ABSTRACT FROM AUTHOR]

The short cycle life of Ni-based cathode materials, especially at the high cut-off voltage, is recognized as one of the major hurdles to widespread commercialization. The commonly dopant elements, like Al, Mg, Ti, Zr, Cd, Zn etc., have been in-depth studied to improve electrochemical performances for Ni-rich cathode. However, the Sb as dopant element for Ni-rich cathode materials has rarely been reported. In this work, the Ni-rich cathode material LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) with Sb doping to bulk and Sb 2 O 3 coating to surface is successfully prepared by adjusting the amount of introduced Sb 2 O 3 in high temperature solid-state reaction process. As a result, Sb-modified NCM811 with Sb doping and Sb 2 O 3 coating exhibits capacity of 176 mAh·g−1 with retention reaching 89.3% at 1 C over 3.0–4.4 V at 55 °C after 100 cycles, whereas the bare NCM811 only delivers 151 mAh·g−1 with the retention of 77.0%. The improvement of cyclability is attributed to synergetic effects of Sb modification. This study reflects Sb modification is an effective method for enhancing cycle life of Ni-rich layered cathode materials. • Sb-modified LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode is synthesized by high temperature solid-state reaction method. • Bulk Sb doping increases the occupied percentage of Ni in Li layer and enlarges the lithium slab spacing I(LiO 2). • Surface Sb 2 O 3 coating protects the active material from electrolyte eroding. • The synergetic effects of Sb modification contributes to the superior cycle performances of NCM811. [ABSTRACT FROM AUTHOR]

Abstract Involving more nickel proportion in Ni-rich cathodes, edging to LiNiO 2 , is an inevitable trend to satisfy the demand of high energy density in lithium-ion batteries, but an inducement for the severer formation of undesirable lithium residues. To overcome the consequent degradation behaviors, a LiCoO 2 @Co 3 O 4 complex coating layer is successfully realized on the surface of LiNiO 2 via a facile wet-chemical method taking advantage of the Li-reactive ability of Co 3 O 4. As a result, the 0.4 wt.% Co modified material exhibits competitively enhanced cyclic performance with 178.1 mAh g−1 after 50 cycles at 1 C, 11% higher than the pristine one in retention rate. Even at higher rates and temperature, it shows better electrochemical stability as well. The superior electrochemical properties of LiCoO 2 @Co 3 O 4 coated LiNiO 2 is ascribed to the dual-function of the coating method, where Co 3 O 4 is formed during heat treatment and simultaneously reacted with surface lithium residues to generate LiCoO 2. In combination of bulk and surface characterization, the significant effects of the coating layer on stabilizing material interface and strengthening the kinetic characteristics for LiNiO 2 cathode materials are investigated and elucidated in detail. [ABSTRACT FROM AUTHOR]

LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) is regarded as one of the promising Li-ion battery cathode materials due to the high capacity and low cost, but the poor cyclic and rate performances hinder its widespread application. In our research, La and Al co-modified NCM811 is successfully prepared by a simple method. XRD and XPS confirm that La and Al can not only dope into the NCM811 bulk, but also form the La 2 Li 0.5 Al 0.5 O 4 coating layer on the surface. The La 2 Li 0.5 Al 0.5 O 4 coated and La-and-Al-doped NCM811 exhibits an excellent capacity retention of 97.2% at 1C in the voltage range of 3.0–4.4 V after 100 cycles, 18.5% higher than that of the pristine. As for rate performance, it exhibits a retention of 95.1% in capacity at 5C after 80 cycles from 3.0 V to 4.4 V, 6.4% higher than that of the pristine. The enhanced high-voltage electrochemical performances are mainly ascribed to the facts that the La and Al strengthen the bulk structure by co-doping and the formed La 2 Li 0.5 Al 0.5 O 4 coating layer, as the high-Tc superconducting oxides, not only promotes the diffusion of Li+ but also protect the cathodes from eroding by with the electrolyte. Meanwhile, the residual lithium is reduced by the formation of La 2 Li 0.5 Al 0.5 O 4. The enhanced electrochemical performance shows that the modification of La 2 Li 0.5 Al 0.5 O 4 coating and La–Al co-doping is a competitive method for industrial production of NCM811 material. • The La–Al co-doping and La 2 Li 0.5 Al 0.5 O 4 coating NCM811 cathode material was prepared by a simple method. • The La and Al were doped in the host material uniformly. • La 2 Li 0.5 Al 0.5 O 4 coating protects the active material from electrolyte eroding. • The co-modification method contributes to the superior electrochemical performances of NCM811. [ABSTRACT FROM AUTHOR]