Fracture behavior of solid electrolyte LATP material based on micro-pillar splitting method

The NASICON type solid electrolyte LATP is a promising candidate for all-solid-state Li-ion batteries considering energy density and safety aspects. To ensure the performance and reliability of batteries, crack initiation and propagation within the electrolyte need to be suppressed, which requires knowledge of the fracture characteristics. In the current work, micro-pillar splitting was applied to determine the fracture toughness of LATP material for different grain orientations. The results are compared with data obtained using a conventional Vickers indentation fracture (VIF) approach. The fracture toughness obtained via micro-pillar splitting test is 0.89 ± 0.13 MPa?m^1/2, which is comparable to the VIF result, and grain orientation has no significant effect on the intrinsic fracture toughness. Being a brittle ceramic material, the effect of pre-existing defects on the toughness needs to be considered.     

Effect of SnO–P2O5–MgO glass addition on the ionic conductivity of Li1.3Al0.3Ti1.7(PO4)3 solid electrolyte

NASICON-type structured compounds Li_1+xM_xTi_2-x(PO₄)₃ (M = Al, Fe, Y, etc.) have captured much attention due to their air stability, wide electrochemical window and high lithium ion conductivity. Especially, Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) is a potential solid electrolyte due to its high ionic conductivity. However, its actual density usually has a certain gap with the theoretical density, leading the poor ionic conductivity of LATP. Herein, LATP solid electrolyte with series of SnO–P₂O₅–MgO (SPM, 0.4 wt%, 0.7 wt%, 1.0 wt%, 1.3 wt%) glass addition was successfully synthesized to improve the density and ionic conductivity. The SPM addition change Al/Ti–O bond and P–O bond distances, leading to gradual shrinkage of octahedral AlO₆ and tetrahedral PO₄. The bulk conductivity of the samples increases gradually with SPM glass addition from 0.4 wt% to 1.3 wt%. Both SPM and the second-phase LiTiPO₅, caused by glass addition, are conducive to the improvement of compactness. The relative density of LATP samples increases first from 0 wt% to 0.7 wt%, and then decreases from 0.7 wt% to 1.3 wt% with SPM glass addition. The grain boundary conductivity also changes accordingly. Especially, the highest ionic conductivity of 2.45 × 10^?4 S cm^?1, and a relative density of 96.72% with a low activation energy of 0.34 eV is obtained in LATP with 0.7 wt% SPM. Increasing the density of LATP solid electrolyte is crucial to improve the ionic conductivity of electrolytes and SPM glass addition can promote the development of dense oxide ceramic electrolytes.     

Influence of LiBO2 addition on the microstructure and lithium-ion conductivity of Li1+xAlxTi2−x(PO4)3(x = 0.3) ceramic electrolyte

Concerning the safety problems of conventional Li-ion batteries with liquid electrolytes, it is crucial to develop reliable solid-state electrolytes with high ionic conductivity. Li_1+xAl_xTi_2?x(PO₄)₃ (LATP, x = 0.3) is regarded as one of the most promising solid electrolytes due to its high ionic conductivity and excellent chemical stability to humidity.Herein, a new strategy is proposed for improving the sintering behavior and enhancing the ionic conductivity of LATP by using LiBO₂ as the sintering aid via liquid phase sintering. The as-prepared sample LATP with homogeneous microstructure and high relative density of 97.1% was successfully synthesized, yielding high total ionic conductivity of 3.5 × 10^?4 S cm^?1 and low activation energy of 0.39 eV at room temperature. It was found that the addition of LiBO₂ could effectively enhance the densification and increase the ionic conductivity of LATP electrolyte, proving an effective way to synthesis LATP ceramics by a simple and reliable route.     

Microstructure,ionic conductivity and mechanical properties of tape-cast Li1.5Al0.5Ti1.5P3O12 electrolyte sheets

Free-standing Li_1.5Al_0.5Ti_1.5P₃O₁₂ electrolyte sheets with a thickness of 50–150 μm were prepared by tape casting followed by sintering at 850–1000 °C in air. While a sintering temperature of 850 °C was too low to achieve appreciable densification and grain growth, a peak relative density of 95% was obtained at 920 °C. At higher sintering temperatures, the microstructure changed from a bimodal grain size distribution towards exclusively large grains (> 10 μm), accompanied by a decrease in relative density (down to 86% at 1000 °C). In contrast, ionic conductivity increased with increasing sintering temperature, from 0.1 mS/cm at 920 °C to 0.3 mS/cm at 1000 °C. Sintering behavior was improved by adding 1.5% of amorphous silica to the slurry. In this way, almost full densification (99.8%) and an ionic conductivity of 0.2 mS/cm was achieved at 920 °C.Mechanical characterization was carried out on the almost fully densified material, yielding elastic modulus and hardness values of 109 and 8.7 GPa, respectively. The fracture strength and Weibull modulus were also characterized. The results confirm that densification and reduction of grain size improve the mechanical properties.     

锂离子电池用电解质掺铝磷酸钛锂的研究现状

综述无机固体电解质和NASICON型体系的基础理论,重点介绍掺铝磷酸钛锂(LATP)的制备和掺杂改性研究进展,展望无机固体电解质LATP的发展趋势。LATP的室温离子电导率可超过10~(-4)S/cm,具备实际应用的水平;电极材料与固体电解质固固界面阻抗较大,倍率性能相对较差。     

锂空气电池固体电解质Li_(1+x)Al_xTi_(2-x)(PO_4)_3的制备研究

以Li_2CO_3、Al_2O_3、TiO_2、NH_4H_2PO_4为原料,采用固相烧结法制备锂空气电池固体电解质Li_(1+x)Al_xTi_(2-x)(PO_4)_3(LATP),研究了不同x值、不同烧结温度对电解质性能的影响。通过X射线衍射仪(XRD)、扫描电镜(SEM)和电化学阻抗谱(EIS)对所制备电解质的结构与性能进行表征。结果表明在x值等于0.2时得到纯相的LATP,最佳烧结工艺是350℃保温2 h,600℃保温2 h,1 000℃保温8 h,室温下的电导率为4.89×10~(-5)S/cm。     

Surface modification of Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode materials via a novel mechanofusion alloy route

This study aimed to prepare a composite coating material comprising a solid ionic conductor of lithium aluminum titanium phosphate (Li_1.4Al_0.4Ti_1.6(PO₄)₃, LATP) and porous carbon through a sol-gel method. LiNi_0.8Co_0.1Mn_0.1O₂ (LNCM811) cathode material with dual-functional composite conductors (i.e., LATP@porous carbon), denoted as LATP-PC, was prepared. The dry-coating method, also called the “mechanical-fusion alloy route,” was used to modify Ni-rich LNCM811 cathode materials. X-ray diffraction (XRD), micro-Raman spectroscopy, and X-ray photoelectron spectroscopy confirmed that the LATP ionic conductor generated herein was uniformly deposited on 3D porous carbon and served as a dual-functional composite coating on LNCM811. Furthermore, the capacity retention of LATP-PC@LNCM811 was approximately 85.57% and 80.86% after 100 cycles at −20 °C and 25 °C, respectively. By contrast, pristine LNCM811 had the capacity retention of 78% and 74.96% at −20 °C and 25 °C, respectively. Furthermore, the high-rate capability of the LATP-PC@LNCM811 material was markedly enhanced to 169.81 mAh g⁻¹ at 10C relative to that of pristine LNCM811, which was approximately 137.67 mAh g⁻¹. The electrochemical performance of LNCM811 was enhanced by the uniform dual-conductive composite coating. The results of the study indicate that the LATP-PC@LNCM811 composite material developed herein is a potentially promising material for future high-energy Li-ion batteries.     

固体电解质Li_(1.3)Al_(0.3)Ti_(1.7)(PO_4)_3烧结片的制备与表征

以固相法合成固体电解质Li1.3Al0.3Ti1.7(PO4)3(LATP)粉末。研究了烧结温度以及烧结时间对LATP离子电导率的影响。采用X射线衍射、扫描电子显微镜和交流阻抗技术对材料粉末以及烧结片相组成、结构和离子导电性进行表征。结果表明,900℃条件下合成的粉末为纯相LATP,颗粒均匀,当LATP电解质基片在900℃下烧结4 h,得到的LATP烧结片表面致密光滑,而且离子电导率较高,为3.03×10-4S/cm。     

Enhancing purity and ionic conductivity of NASICON-typed Li1.3Al0.3Ti1.7(PO4)3 solid electrolyte

Increasing demand for safe energy storage and portable power sources has led to intensive investigation for all-solid state Li-ion batteries and particularly to solid electrolytes for such rechargeable batteries. One of the most promising types of solid electrolytes is NASICON-structured Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) due to its relatively high ionic conductivity and stability towards air and moisture. Here, the work is aimed on implementing the steps to hinder formation of impurity phases reported for various synthesis routes. Consequently, the applied modifications in the preparation strategies alter a crystal shape and size of prepared material. These two parameters have an enormous impact on properties of LATP. Fabrication of larger particles with a cubic shape significantly improves its ionic conductivity. As a result, LATP preparation methods such as a solution chemistry and molten flux resulted in the highest ionic conductivity samples with the value of ~10^?4 S cm^?1 at room temperature. Other LATPs obtained by solid-state reaction, sol-gel and spray drying methods depicted the ionic conductivity of ~10^?5 S cm^?1. The activation energy of lithium ion transfer in LATP varied in a range of 0.25–0.4 eV, which is in well agreement with the previously reported data.     

固体电解质的制备及其在锂氧电池性能研究

本文提出了将高离子电导率的全固态电解质Li1.4Al0.4Ti1.6(PO3)4(LATP)用于锂氧电池。用Pechini法成功的合成了全固态电解质，采用X射线荧光衍射(XRD)、场发射扫描电子显微镜(SEM)和电化学性能分析其性能。结果显示，LATP不仅具有较高的离子导电性，而且LATP作为固体电解质，具有更高的放电平台。同时，LATP固体电解质能降低电解质的分解，从而能够减少放电产物的生成。因此，LATP玻璃陶瓷固体用于锂氧电池提高了锂氧电池的热稳定性并且降低了锂氧电池热膨胀。LATP固体电解质利用在可再充电锂氧电池中具有良好的前景。