Search

Most Li+/Na+-conducting solid electrolytes are unstable in moisture, and the formed hydroxides and carbonates on their surfaces result in the increase of the interfacial resistance between solid el...

Ni-rich layered oxides (LiNi1-x-yCoxMnyO2, 1-x-y ≥ 0.5) are attracting great attention due to their high capacity and operating voltage. However, Ni-rich layered oxides still face long-standing challenges, such as incomplete capacity release and fast capacity fade, especially at high C rates. Herein, we implement a wet chemical method to dope Ti into LiNi0.8Co0.1Mn0.1O2 (NCM811). We discover that NCM811 with the homogeneously distributed Ti can effectively enhance ion transfer kinetics and thus greatly improve capacity delivery at high C rates. The Ti-doped NCM811 exhibits a capacity of 196 mAh/g and 157 mAh/g at 0.5C and 2C in voltage range of 2.8–4.6 V, 5% higher (188 mAh/g at 0.5C) and 15% higher (136 mAh/g at 2C) than the pristine NCM811. Ti-doped NCM811 cathodes also exhibit enhanced cycling stability with capacity retention of 84% after 100 cycles at 1C, which shows that our methodology for Ti doping is potentially competitive for a practical production of Ni-rich layered oxides.

Na super ionic conductor (NASICON)-structured materials have evolved to play many critical roles in battery systems because of their three-dimensional framework structures. Here, by coupling NASICON-structured Na3V2(PO4)2O2F cathodes and Na3V2(PO4)3 anodes, an asymmetric Na-ion-based full cell exhibits two flat voltage plateaus at about 2.3 and 1.9 V and a high capacity of 101 mA h/g. Moreover, an all-solid-state Na-ion battery has been further enabled by the concept of using all NASICON-structured materials, including cathodes, anodes, and electrolytes (Na5YSi4O12), which delivers a high output voltage. Importantly, the full cell displays high safety without using a flammable organic liquid electrolyte and superior structure stability with all NASICON-structured materials.

An in-situ prepared binder-free Li 3 V 2 (PO 4 ) 3 /C membrane electrode supported on 3D N-doped carbon fibers (LVP/C@NCF) has been developed. The residual carbon in LVP/C@NCF consists of the pyrolytic carbon from glucose and the N-doped carbon fibers decomposed from filter paper. The former uniformly covers on the surface of LVP particles, while the latter is functioned as both a 3D conductive network and a current collector for LVP. Compared with the traditional LVP/C electrode supported on Al foil (LVP/C@Al), the LVP/C@NCF membrane electrode displays higher rate capability and better cycle stability. Especially, when cycled at a high rate of 10 C, it still delivers a specific capacity as high as 107.6 mA h g −1 with a very low capacity fading ratio of ~0.0048% per cycle after 1000 cycles. The excellent electrochemical performance is ascribed to the synergetic effect from the 3D effectively conductive network and the in-situ produced current collector of carbon fibers. The method of using filter paper as the source of carbon and current collector to prepare integrated membrane electrode may provide feasible and effective strategy to fabricate binder-free flexible and lightweight lithium ion batteries as well as sodium ion batteries.

Elemental doping represents a prominent strategy to improve interfacial chemistry in battery materials. Manipulating the dopant spatial distribution and understanding the dynamic evolution of the dopants at the atomic scale can inform better design of the doping chemistry for batteries. In this work, we create a targeted hierarchical distribution of Ti

Li3V2(PO4)3/C (LVP/C) composites have been modified by different ways of Zr-incorporation via ultrasonic-assisted solid-state reaction. The difference in the effect on the physicochemical properties and the electrochemical performance of LVP between Zr-doping and ZrO2-coating has also been investigated. Compared with pristine LVP/C, Zr-incorporated LVP/C composites exhibit better rate capability and cycling stability. In particular, the LVP/C-Zr electrode delivers the highest initial capacity of 150.4 mA h g−1 at 10C with a capacity retention ratio of 88.4% after 100 cycles. The enhanced electrochemical performance of Zr-incorporated LVP/C samples (LVZrP/C and LVP/C-Zr) is attributed to the increased ionic conductivity and electronic conductivity, the improved stability of the LVP structure, and the decreased charge-transfer resistance.

A novel Li 3 V 2 (PO 4 ) 3 composite modified with Fe-doping followed by C+SiO 2 hybrid layer coating (LVFP/C-Si) is successfully synthesized via an ultrasonic-assisted solid-state method, and characterized by XRD, XPS, TEM, galvanostatic charge/discharge measurements, CV and EIS. This LVFP/C-Si electrode shows a significantly improved electrochemical performance. It presents an initial discharge capacity as high as 170.8 mA h g −1 at 1 C, and even delivers an excellent initial capacity of 153.6 mA h g −1 with capacity retention of 82.3% after 100 cycles at 5 C. The results demonstrate that this novel modification with doping followed by hybrid layer coating is an ideal design to obtain both high capacity and long cycle performance for Li 3 V 2 (PO 4 ) 3 and other polyanion cathode materials in lithium ion batteries.

Development of the next-generation, high-energy-density, low-cost batteries will likely be fueled by sodium (Na) metal batteries because of their high capacity and the abundance of Na. However, their practical application is significantly plagued by the hyper-reactivity of Na metal, unstable solid electrolyte interphase (SEI), and dendritic Na growth, leading to continuous electrolyte decomposition, low Coulombic efficiency, large impedance, and safety concerns. Herein, we add a small amount of SnCl2 additive in a common carbonate electrolyte so that the spontaneous reaction between SnCl2 and Na metal enables in situ formation of a Na–Sn alloy layer and a compact NaCl-rich SEI. Benefitting from this design, rapid interfacial ion transfer is realized and direct exposure of Na metal to the electrolyte is prohibited, which jointly achieve a nondendritic deposition morphology and a markedly reduced voltage hysteresis in a Na/Na symmetric cell for over 500 h. The Na/SnCl2-added electrolyte/Na3V2(PO4)3 full cel...

Monoclinic Li3V2(PO4)3/C (LVP/C) and Li3V1.95Fe0.05(PO4)3/C (LVFP/C) composites were successfully modified by cobalt incorporation. The effects of cobalt incorporation on the structure, morphology and electrochemical performance of the LVP/C and LVFP/C composites were systematically investigated. The results show that most Co exists in the form of CoO and forms a hybrid layer with the carbon coating on the surface of the LVP and LVFP particles; moreover, a small part of Co enters into the LVP or LVFP lattices due to atomic diffusion. Compared with LVP/C and LVFP/C, Co-incorporated samples exhibit better electrochemical performance. In particular, under the common effect of doping and a hybrid layer (carbon and metal oxides) coating, the LVFP/C-Co electrode displays a prominent initial capacity of 124.7 mA h g−1 and a very low capacity fading of ∼0.04% per cycle even after 500 cycles at 20 C. This novel co-modification method with cation doping and a hybrid layer (carbon and metal oxide) coating is a highly effective way to improve the electrochemical performance and has great potential to be easily used to modify other cathode materials with poor electrical conductivity.

Reduced graphene oxide (rGO) incorporated Li3V1.94Fe0.06(PO4)3/C cathode materials were successfully prepared by a sol–gel method. Compared with Li3V2(PO4)3/C and single rGO-incorporated Li3V2(PO4)3/C, the rGO-incorporated Li3V1.94Fe0.06(PO4)3/C electrode has the highest initial capacity of 164.4 mA h g−1 with a capacity retention ratio of 83.5% after 100 cycles at 1C. When charged/discharged for 1000 cycles at 5C, it exhibits a prominent capacity of 129.3 mA h g−1 with a capacity retention ratio of 91.5% and a very low capacity fading of 0.0085% per cycle. The superior electrochemical performance of Fe-doped and rGO-incorporated Li3V2(PO4)3 can contribute to the reduced particle size, the improved electronic conductivity, and the increased Li-ion diffusion coefficient. We believe this novel co-modification with Fe-doping and rGO-incorporation is an efficient way for Li3V2(PO4)3 and any other polyanion cathode materials to realize their application in power lithium ion battery.

Natural graphite treated by mechanical activation can be directly applied to the preparation of Li3V2(PO4)3. The carbon-coated Li3V2(PO4)3 with monoclinic structure was successfully synthesized by using natural graphite as carbon source and reducing agent. The amount of activated graphite is optimized by X-ray diffraction, scanning electron microscope, transmission electron microscope, Raman spectrum, galvanostatic charge/discharge measurements, cyclic voltammetry, and electrochemical impedance spectroscopy tests. Our results show that Li3V2(PO4)3 (LVP)-10G exhibits the highest initial discharge capacity of 189 mAh g−1 at 0.1 C and 162.9 mAh g−1 at 1 C in the voltage range of 3.0–4.8 V. Therefore, natural graphite is a promising carbon source for LVP cathode material in lithium ion batteries.

All-solid-state lithium batteries (ASSLBs) have the potential to revolutionize battery systems for electric vehicles due to their benefits in safety, energy density, packaging, and operable temperature range. As the key component in ASSLBs, inorganic lithium-ion-based solid-state electrolytes (SSEs) have attracted great interest, and advances in SSEs are vital to deliver the promise of ASSLBs. Herein, a survey of emerging SSEs is presented, and ion-transport mechanisms are briefly discussed. Techniques for increasing the ionic conductivity of SSEs, including substitution and mechanical strain treatment, are highlighted. Recent advances in various classes of SSEs enabled by different preparation methods are described. Then, the issues of chemical stabilities, electrochemical compatibility, and the interfaces between electrodes and SSEs are focused on. A variety of research addressing these issues is outlined accordingly. Given their importance for next-generation battery systems and transportation style, a perspective on the current challenges and opportunities is provided, and suggestions for future research directions for SSEs and ASSLBs are suggested.