Improved Cycling Stability of Cobalt-free Li-rich Oxides with a Stable Interface by Dual Doping

Li-rich cobalt-free oxides, popularly used as a cathode with high capacity in lithium ion battery, always suffer from poor cycling stability between 2.0 and 4.8 V vs Li+/Li, especially when cycled at high temperatures (>50 \ub0C). To overcome this issue, Na+ and Al3+ dual-doped NaxLi1.2-xMn0.6-xAlxNi0.2O2 Li-rich cathode is prepared in this study. It is shown that the side reactions between cathode and electrolyte during cycling are suppressed. The improved cycling performance is observed for all of the doped samples, among which the sample with x = 0.03 exhibits the highest capacity retention of 86.1% after 200 cycles between 2.0 and 4.8 V at 2C (1C = 200 mA g−1) and shows a remarkable cycling stability, even at a high temperature of 55 \ub0C (a capacity retention of 92.2% after 100 cycles). Moreover, the average voltage of the sample with x = 0.03 after 100 cycles at 0.5C remains at 3.11 V with a retention ratio of 86.6%. This work provides a new strategy to develop Li-rich cobalt-free cathodes with excellent cycling stability for lithium ion batteries at high temperatures

Balancing stability and specific energy in Li-rich cathodes for lithium ion batteries: a case study of a novel Li–Mn–Ni–Co oxide

Lithium batteries for UPS, portable electronics and electrical vehicles rely on high-energy cathodes. Li-rich manganese-rich oxide (xLi2MnO3\ub7(1 − x)LiMO2, M = transition metals) is one of the few materials that might meet such a requirement, but it suffers from poor energy retention due to serious voltage and/or capacity fade, which challenges its applications. Here we show that this challenge can be addressed by optimizing the interactions between the components Li2MnO3 and LiMO2 in the Li-rich oxide (i.e. stabilizing the layered structure through Li2MnO3 and controlling Li2MnO3 activation through LiMO2). To realize this synergistic effect, a novel Li2MnO3-stabilized Li1.080Mn0.503Ni0.387Co0.030O2 was designed and prepared using a hierarchical carbonate precursor obtained by a solvo/hydro-thermal method. This layered oxide is demonstrated to have a high working voltage of 3.9 V and large specific energy of 805 W h kg−1 at 29 \ub0C as well as impressive energy retention of 92% over 100 cycles. Even when exposed to 55 \ub0C, energy retention is still as high as 85% at 200 mA g−1. The attractive performance is most likely the consequence of the balanced stability and specific energy in the present material, which is promisingly applicable to other Li-rich oxide systems. This work sheds light on harnessing Li2MnO3 activation and furthermore efficient battery design simply through compositional tuning and temperature regulation

An advanced construction strategy of all-solid-state lithium batteries with excellent interfacial compatibility and ultralong cycle life

The inferior cycle performance of All-solid-state lithium batteries (ASSLBs) resulting from the low mixed ionic and electronic conductivity in the electrodes, as well as the large interfacial resistance between the electrodes and the electrolyte need to be overcome urgently for commercial applications. Here, an advanced cell construction strategy has been proposed, in which a cohesive and highly conductive poly(oxyethylene) (PEO)-based electrolyte is employed both in the cathode layer and in the interface of the electrolyte/anode, leading to an ASSLB with superior interfacial contact between the electrolyte and the electrodes, and forming a three-dimensional ionic conductive network in the cathode layer. Especially, the NASICON-type ionic conductor covered with the PEO-based polymer, integrating the advantages of an inorganic electrolyte and organic electrolyte, presents an enhanced electrochemical stability and an excellent compatibility with the Li electrode. Consequently, the ASSLBs of LiFePO4 (LFP)/Li with this advanced construction strategy exhibit excellent interfacial compatibility, ultralong cycle life and high capacity, i. e., a reversible discharge capacity maintained at 127.8 mA h g(-1) for the 1000th cycle at 1C with a retention of 96.6%, and an initial discharge capacity of 153.4 mA h g(-1) with a high retention of 99.9% after 200 cycles at 0.1C. Besides, the high-voltage monopolar stacked batteries with a bipolar structure can be fabricated conveniently, showing an open circuit voltage (OCV) of 6.63 V with a good cycle performance. In particular, the ASSLBs present outstanding safety in terms of nail penetration and burning in fire. Therefore, this advanced cell construction strategy may generate tremendous opportunities in the search for novel emerging solid-state lithium metal batteries

High ion conductive Sb2O5-doped beta-Li3PS4 with excellent stability against Li for all-solid-state lithium batteries

The combination of high conductivity and good stability against Li is not easy to achieve for solid electrolytes, hindering the development of high energy solid-state batteries. In this study, doped electrolytes of Li3P1-xSbxS4-2.5xO2.5x are successfully prepared via the high energy ball milling and subsequent heat treatment. Plenty of techniques like XRD, Raman, SEM, EDS and TEM are utilized to characterize the crystal structures, particle sizes, and morphologies of the glass-ceramic electrolytes. Among them, the Li3P0.98Sb0.02S3.95O0.05 (x = 0.02) exhibits the highest ionic conductivity (similar to 1.08 mS cm(-1)) at room temperature with an excellent stability against lithium. In addition, all-solid-state lithium batteries are assembled with LiCoO2 as cathode, Li10GeP2S12/Li3P0.98Sb0.02S3.95O0.05 as the bi-layer electrolyte, and lithium as anode. The constructed solid-state batteries delivers a high initial discharge capacity of 133 mAh g(-1) at 0.1C in the range of 3.0-4.3 V vs. Li/Li+ at room temperature, and shows a capacity retention of 78.6% after 50 cycles. Most importantly, the all-solid-state lithium batteries with the Li10GeP2S12/Li3P0.98Sb0.02S3.95O0.05 electrolyte can be workable even at - 10 degrees C. This study provides a promising electrolyte with the improved conductivity and stability against Li for the application of all-solid-state lithium batteries

High ion conductive Sb2O5-doped beta-Li3PS4 with excellent stability against Li for all-solid-state lithium batteries

The combination of high conductivity and good stability against Li is not easy to achieve for solid electrolytes, hindering the development of high energy solid-state batteries. In this study, doped electrolytes of Li3P1-xSbxS4-2.5xO2.5x are successfully prepared via the high energy ball milling and subsequent heat treatment. Plenty of techniques like XRD, Raman, SEM, EDS and TEM are utilized to characterize the crystal structures, particle sizes, and morphologies of the glass-ceramic electrolytes. Among them, the Li3P0.98Sb0.02S3.95O0.05 (x = 0.02) exhibits the highest ionic conductivity (similar to 1.08 mS cm(-1)) at room temperature with an excellent stability against lithium. In addition, all-solid-state lithium batteries are assembled with LiCoO2 as cathode, Li10GeP2S12/Li3P0.98Sb0.02S3.95O0.05 as the bi-layer electrolyte, and lithium as anode. The constructed solid-state batteries delivers a high initial discharge capacity of 133 mAh g(-1) at 0.1C in the range of 3.0-4.3 V vs. Li/Li+ at room temperature, and shows a capacity retention of 78.6% after 50 cycles. Most importantly, the all-solid-state lithium batteries with the Li10GeP2S12/Li3P0.98Sb0.02S3.95O0.05 electrolyte can be workable even at - 10 degrees C. This study provides a promising electrolyte with the improved conductivity and stability against Li for the application of all-solid-state lithium batteries

A Study on Storage Characteristics of Pristine Li-rich Layered Oxide Li1.20Mn0.54Co0.13Ni0.13O2: Effect of Storage Temperature and Duration

Lithium-ion batteries always suffer from serious capability decay, especially when stored at high temperature and/or for prolonged duration. In this work, electrochemical performance for Li-rich layered oxides Li1.20Mn0.54Co0.13Ni0.13O2 was systematically investigated as a function of temperature and duration. Plenty of techniques like SEM, EDS, EIS, ARC, Raman, XRD, and XPS were utilized to characterize the structures, valence states, compositions, particle sizes, and morphologies of the layered oxides with varying temperature and duration. The results reveal that room temperature storage may alter surface kinetics, but hardly influence the electrochemical performance. While in the case of high temperature storage in pristine state, cycling stability is highly dependent on the storage duration. The degradation mechanism at high temperature storage with prolonged duration is demonstrated to be the accumulation of surface species like LiF/LixPFyOz initiated by the strong reactions between LiPF6 electrolyte and electrode. The results reported here may shed light on predicting electrochemical performance by surface analysis and also provide vital hints on enhancing the high-temperature storage stability of Li-rich layered oxides

Hollow porous silicon nanospheres with 3D SiC@C coating as high-performance anodes

Silicon is regarded as one of the most promising anode candidates for next-generation Li-ion batteries because of its high theoretical capacity (4200 mAh g−1). However, the main challenge for the practical application of Si anodes is the huge volume change during (de)alloying with lithium, which leads to the pulverization of the active material and severe loss of electrical contact after cycling. Here, we develop hollow porous silicon nanospheres with three-dimensional carbon coating and SiC transition interlayer (C@SiC@Si@SiC@C) via a simple and straightforward polymer-directed strategy in order to tackle the challenges met with Si anodes. The accordingly synthesized C@SiC@Si@SiC@C anode shows high utilization of the active substance, high measured capacity (3200 mAh g−1) with almost 100% Coulombic efficiency and stable cycling performance (0.7‰ per cycle decay rate at 0.2C). Such superior performances are related to the uniquely designed structure. Firstly, the 3D carbon coating provides high electronic conductivity, and extremely small size of silicon shortens the diffusion distance for Li ions and electrons. Secondly, the stable cyclability originates from the nanoscale silicon particles reinforced by a SiC transition interlayer which effectively prevents fracture and provides robust outer layers, respectively