Garnet Li7La3Zr2O12 (LLZO) is an attractive and highly promising solid electrolyte, has made a significant progress in the battery performance to achieve higher energy density and better safety. However, the poor wettability between the interface of garnet and Li metal anode leads to high interfacial impedance and the penetration of Li dendrites during cycling, which limits the practical application of garnet. Polishing treatment is a very simple and convenient physical treatment method for the surface of garnet. Here, we investigate the effects of surface treatment of Li6.25Al0.2La3Zr2O11.85Br0.15 (LALZOBr0.15) with different grit sizes of sandpaper on the wettability and interfacial resistance between it and Li metal. Compared to coarse and very fine sandpaper, the LALZOBr0.15-600 electrolyte polished with 600-grit sandpaper was significantly reduced the interfacial impedance to 20.9 ohm cm2, ensuring tight contact at the Li|LALZOBr0.15-600 interface, thereby further inhibiting the growth of Li dendrites. Moreover, benefiting from the excellent interface, Li|LALZOBr0.15-600|Li symmetric cell exhibited an excellent cycling stability and could be cycled at 0.3 mA cm-2 over 1300 cycles without short-circuiting. Applying it to quasi-solid-state batteries and all-solid-state batteries, which also showed great elec-trochemical performance. Our work demonstrates the importance of using a moderate grit sandpaper for elec-trolyte surface treatment.

Cubic garnet Li7La3Zr2O12 (LLZO) solid electrolytes have a strong potential to allow solid-state lithium-ion to become the next-generation energy storage systems and for addressing the safety issues. However, the applications of LLZO solid electrolytes are seriously limited by the relatively low critical current density of LLZO. In this study, we introduce lithium bromide (LiBr) with a low melting point as the sintering aid to prepare a high-performance garnet with high ionic conductivity, high relative density, and excellent critical current density. The prepared LLZO solid electrolyte with a LiBr concentration of 0.15 (xLiBr-LLZO with x = 0.15 mol) exhibited a high ionic conductivity of 7.62 x10(-4) S cm(-1) at 25 degrees C with an excellent relative density of 96.27%. The critical current density (CCD) of the symmetric Li vertical bar 0.15LiBr-LLZO vertical bar Li cell was 1.0 mA cm-2 at 25 degrees C. Furthermore, this cell can stably operate for 10 00 h under a current density of 0.3 mA cm(-2). In addition, quasi-solid-state batteries of Li vertical bar LiFePO4 with 0.15LiBr-LLZO electrolyte delivered excellent capacity retention (141.1 mAh g(-1); similar to 89.7%) after 300 cycles, excellent rate performance, high coulombic efficiency and cycling stability. Furthermore, Li vertical bar LiNi0.8Co0.1Mn0.1O2 with 0.15LiBr-LLZO electrolyte could run normally with high coulombic efficiency (>99%). These research results show that the solid-state batteries developed using 0.15LiBr-LLZO electrolyte are highly promising for the practical applications. (C) 2022 Elsevier Ltd. All rights reserved.

LiFePO4 with ultrahigh rate ability and enhanced electronic/ionic conductivity can be achieved by element doping. However, the role of substitution on the electronic/ionic conductivity and size effect on the electrochemical performance are still open. Here, LiFePO4 particles (LC-LFP) with tuned sizes are synthesized via La and Ce co-doping, delivering a capacity of 91.9 mAh g-1 under 200 C. In addition, LC-LFP exhibit a power density as high as 57.6 kW kg-1 when the energy density is nearly 300 Wh kg-1 owing to the 105 enhancement of inherent conductivity and 105 Li+ diffusion ability. DFT results suggest that La and Ce co-doping would not only facilitate free Li+ ions to extrude out of the unit cell due to the structure distortion but also generate extra middle-gap states to boost the carrier concentration. Furthermore, it appears that atoms on the surface of the particles tend to decrease the band gap and lower the conduction band compared to the atoms in the bulk. This work demonstrates and discloses a promising strategy to enhance the rate performance of LiFePO4 element co-doping.

Garnet-type solid-state electrolyte Li7La3Zr2O12 (LLZO) is expected to realize the next generation of high-energy-density lithium-ion batteries. However, the severe dendrite penetration at the pores and grain boundaries inside the solid electrolyte hinders the practical application of LLZO. Here, it is reported that the desirable quality and dense garnet Li6.8Al0.2La3Zr2O11.80F0.20 can be obtained by fluoride anion doping, which can effectively facilitate grain nucleation and refine the grain; thereby, the ionic conductivity increased to 7.45 × 10-4 at 30 °C and the relative density reached to 95.4%. At the same time, we introduced a transition layer to build the Li6.8Al0.2La3Zr2O11.80F0.20-t electrolyte in order to supply a stable contact; as a result, the interface resistance of Li|Li6.8Al0.2La3Zr2O11.80F0.20-t decreases to 12.8 Ω cm2. The Li|Li6.8Al0.2La3Zr2O11.80F0.20-t|Li symmetric cell achieved a critical current density of 1.0 mA cm-2 at 25 °C, which could run stably for 1000 h without a short circuit at 0.3 mA cm-2 and 25 °C. Moreover, the Li|LiFePO4 battery exhibited a high Coulombic efficiency (>99.5%), an excellent rate capability, and a great capacity retention (123.7 mA h g-1, ≈80%) over 500 cycles at 0.3C and 25 °C. The Li|LiNi0.8Co0.1Mn0.1O2 cell operated well at 0.2C and 25 °C and delivered a high initial discharge capacity of 151.4 mA h g-1 with a good capacity retention (70%) after 195 cycles. This work demonstrates that the anion doping in LLZO is an effective method to prepare a dense garnet ceramic for the high-performance lithium batteries.

Many strategies have been employed to enhance the electrical conductivity and lithium ion diffusion of LiFePO4 under hydrothermal method. But the modification of the crystal structure affected by preparation technology as well as the influence of the modification on the electrochemical performance at low temperature are not fully understood. This paper systematically reports the LiFePO4/graphene nanocomposites synthesized with different preparing techniques. Among the four methods employed, LiFePO4/graphene nanocomposites synthesized by stirring and dropping method obtains smaller potential difference, less charge transfer resistance and reduced polarization resulting from larger interplanar spacing, less Fe-Li anti-site defects and higher conductivity. The systematical study of charge transfer resistance, Li+ diffusion coefficient, capacity and activation energy at 2.5 - 4.3 V from -30 - 50 degrees C indicates that compared with charge transfer process, lithium ion diffusion is the rate-determining step and that there is a transition from semi-infinite diffusion-controlled behavior to surface-controlled energy storage process as the temperature drops. The as-prepared sample acquires enhanced discharge capacity as high as 93.6 mAh g(-1) (0.5 C) at -30 degrees C and better rate performance both. Simulation reveals that the lithium ion diffusion process is substantially impeded at low temperature resulting in uneven Li+ distribution in the electrode. (C) 2020 Published by Elsevier Ltd.

Solid garnet electrolyte Si-Li7La3Zr2O12 (LLZO) based Li metal batteries is a promising candidate for the next generation high energy device due to the advantages of electrochemical stability and relative high ionic conductivity at mom temperature (10(-4) S cm(-1)). Here, a series of xSi-LLZO electrolytes are prepared by the traditional solid state sintering. The 0.15 Si-LLZO result shows the maximum Li ionic conductivity (6.68 x 10(4) S cm(-1), 25 degrees C) and minimum electronic conductivity (4.41 x 10(-8) S cm(-1), 25 degrees C), meanwhile tactfully formes LLZO@LiAlSi2O6 (LLZO@LAS) electrolyte in this process. The hard-to-hard poor contact, resulting in a very large interfacial resistance and low Coulombic efficiency in Li metal bettries. Herein, we demonstrate a simple and effective to overcome the interfacial obstacles by introducing polymer poly(ethylene oxide) (PEO) electrolyte thin buffer layer to modify the bare garnet electrolyte, forming a P-0.15 Si-LLZO-P composite electrolyte. The integrated NCM811/P-0.15 Si-LLZO-P/Li and LFP/P-0.15 Si-LLZO-P/Li batteries show a high Coulombic efficiency of around 99.0% and 98.5% at 50 degrees C, respectively. Meanwhile, P-0.15 Si-LLZO-P composite electrolyte stays intact after cycling. In all, construcing a polymer interfacial modifacation is an convenient and effective way to realize all solid-state Li metal batteries.

An advanced cathode material paired with Li metal anode that possesses superior energy density and cycling stability under high rate is critical for the development of lithium ion batteries (LIBs). Herein, by employing LiVPO4F (LVPF) as a model cathode paired with Li metal anode, we demonstrate an effective strategy to simultaneously address the issues of lattice disorder of the cathode and inhomogeneous deposition of Li+ on the Li metal anode during long-term cycling. A marginal amount of big radius Nathorn and high-valence Nb5+ ions are introduced at the Li and V site, respectively, to act as pillars to stabilize the lattice and form donor doping to improve the electronic conductivity of LVPF. With such a dual-site substitution strategy, the carbon coated cathode material with a composition of Li0.993Na0.007V0.98Nb0.02PO4F (denoted as LVPF-NN@C) paired with Li metal anode delivers an initial discharge energy density of 398.2 Wh kg(-1) with a retention rate of 86.0% after 2500 cycles at 10 C. Through systematically analyzing and comparing the LVPF-NN@C parallel to Li cell with the undoped counterpart (LVPF@ C||Li cell), it confirms that the superior cycling stability of the LVPF-NN@C||Li cell originates from the sustainable low resistance and high Li+ diffusivity during long-term cycling, the great chemical and structural stability of LVPF-NN@C, and the homogeneous deposition of Lithorn on Li metal surface. These results may provide a valuable guidance to other cathode materials as well for designing advanced LIBs. (c) 2020 Elsevier Ltd. All rights reserved.

Antisite defects in LiFePO4 and LiNi1/3Co1/3Mn1/3O2 cathode materials will severely decrease Li+ diffusion ability and the cell capacity. However, the mechanism of constraining antisite defects dur...

For portable and wearable electronics, a flexible full battery can lead to tremendous development. However, certain issues with the anode still exist, such as complexity, low capacity, and poor stability. Herein, a flexible metal oxide (MOx) composite anode is synthesized in situ, which transfers a stainless‐steel mesh (SSM) to the SSM‐MOx‐900@PPy anode, with void‐array MOx nanoframeworks encapsulated within polypyrrole (PPy). The hierarchical structure offers a close connection and highly interpenetrated porous conductive network between PPy and MOx, which sufficiently constrains the volume changes and enhances the electronic conductivity. Besides, the binder‐free connection between the active material and current collector is effective for charge transport and robust structural stability during the electrochemical processes. The prepared SSM‐MOx@PPy anode exhibits low contact resistance, decreased charge transfer resistance, and enhanced Li+ diffusion coefficient, resulting in an ultrahigh capacity of 1000 mAh g−1 at 0.1 C and outstanding cycling stability of 640.9 mAh g−1 with a retention rate of 99% after 100 cycles at 1 C. The high‐power full battery fabricated by the SSM‐MOx‐900@PPy and LiFePO4 can be bent and folded freely without obvious capacity attenuation (99.2% of the initial value after 100 bending cycles). These results may provide valuable guidance for designing advanced anodes.

Na super ion conductor (NASICON) Na3Zr2Si2PO12 (NZSP) is considered to be one of the most promising solid electrolytes for solid-state sodium batteries. However, low ionic conductivity is one of the main challenges for its practical application. Herein, we report a novel Mg2+/F- co-assisting strategy to synthesize NZSP solid electrolyte with enhanced ionic conductivity. Mg2+/F- co-assisting leads to a significant increase in the particle size and a reduction in the concentration of grain boundary. A dense microstructure is also formed with co-assisting. Consequently, high ionic conductivity of 2.21 mS cm(-1) at 300 K, low electronic conductivity of 1.76x10(-5) mS cm(-1) at 300 K and low activation energy of similar to 0.27 eV are achieved for the optimized Mg2+/F- co-assisted NZSP solid electrolyte. Finally, a Na/Na3V2(PO4)(3) solid-state sodium battery employing Mg2+/F- co-assisted NZSP solid electrolyte exhibits an excellent electrochemical performance. High discharge specific capacity of 71.5 mAh g(-1) is displayed at 1 C at 300 K, with 96 % retention after 100 cycles. Therefore, this cation/anion co-assisting strategy provides inspiration for the development of other classes of ceramic solid electrolytes for solid-state sodium batteries.

Simultaneous realization of superior energy density and cyclic stability of a cathode material under high rate is imperative for practical applications in rechargeable lithium-ion batteries (LIBs). In the present work, the effects of a marginal amount of K substitution of Li on the electrochemical properties of the Li1-xKxV0.98Nb0.02PO4F@C (L1-xKxVNPF@C, x = 0-0.01) cathode materials are investigated. As a result, K substitution of Li has a great influence on the electronic conductivities, ionic conductivities, charge transfer resistances, and Li+ diffusion coefficients of the L1-xKxVNPF@C (x = 0.003-0.01) cathode materials. Substantially improved discharge capacities and energy densities are observed in the L1-xKxVNPF@C (x = 0.003-0.01) cathodes under high charge/discharge current densities of 0.4-1 A g(-1). In particular, because of the highest Li+ conductivity and diffusivity, the L0.995K0.005VNPF@C cathode exhibits an optimal electrochemical performance at both 25 and 50 degrees C. It delivers a high discharge capacity of 101 mA h g(-1) at 10 C with a capacity retention of 95.3% after 1000 cycles at 25 degrees C. Correspondingly, the initial discharge energy density and energy retention is 396.2 Wh kg(-1) and 96.4%, respectively. Even evaluated at 9 C and 50 degrees C, the initial discharge energy density and energy retention after 500 cycles is 420.6 Wh kg(-1) and 92.9%, respectively, which is highly promising for practical applications. The present work may provide a valuable guidance to elevate the energy density and cyclic stability of a cathode material for high-rate LIBs.

F−-assisted Na3Zr2Si2PO12 (NZSP) solid electrolyte with high ionic conductivity is promising as a solid electrolyte for solid-state sodium batteries.

Dual-site magnesium doping is successfully utilized to enhance the electrochemical performance of Li2MnSiO4/C/rGO. Both Li-site and Mn-site Mg doping decline the particle sizes and stretch Li-O bond, resulting in the improved Li+ diffusivity by over one order of magnitude. The Li-site Mg doping increases the carrier mobility and reduces the band gap of Li2MnSiO4, leading to the improved electronic conductivity. Additionally, the Mn-site Mg doping eases the volume change of Li2MnSiO4 during Li+ extraction and insertion, which contributes to the enhanced structural stability. Consequently, Li1.98Mg0.02Mn0.94Mg0.06SiO4/C/rGO composite delivers a high initial discharge capacity of 258.0 mA h g(-1) and retain 206.7 mA h g(-1) after 50 cycles at C/16 rate between 1.5 V and 4.7 V. More importantly, its discharge capacity is increased by 25.9% to 178.4 mA h g(-1) at C/2 rate, compared with Li2MnSiO4/C/rGO composite. Besides, its capacity retention is as high as 90.3% after 100 cycles.