No abstract

A novel and facile method for the preparation of monolithic LiFePO 4 /carbon composites with well-defined macropores has been developed. The precursor macroporous gels consisting of inorganic networks as well as organic polymers were fabricated by the epoxide-mediated sol−gel method accompanied by phase separation. The inorganic−organic hybrid gels were calcined under an inert atmosphere, resulting in LiFePO 4 /carbon monoliths. The influence of the starting compositions on the gel morphologies has been investigated, and the constituents of the gel network were discussed. The reaction mechanism of the crystallization of LiFePO 4 from green bodies during calcination has also been investigated by thermal analysis, X-ray diffraction, and Raman scattering. In addition, the electrochemical properties of the resultant LiFePO 4 /carbon composites were examined by the charge−discharge test.

materials generates volume changes. [2,3] In conventional lithium-ion batteries (LiBs) employing liquid electrolytes, volume expansion dissipates in the electrode matrix (carbon/binder) and depends only on the intrinsic properties of the active material. [4,5] The mechanical fracture of the active material particles and mechanical disintegration of the electrode might be even more severe for all-solid-state batteries (SSBs) as the battery needs to maintain its mechanical integrity for proper cycling.Research in the field of SSBs is motivated by their promised high power and energy density on the cell level compared to conventional LiBs. [6] In particular, inorganic glassy and ceramic solid electrolyte (SE), for example, the thio-LiSICON family [6][7][8] and garnet-type (Li 5 La 3 M 2 O 12 ) conductors, [9] with high room-temperature ionic conductivity up to 10 mS cm −1 , moved the performance of SSBs close to and beyond that of the state-of-the-art LiB. [6] Among all superionic conductors, amorphous Li 2 S-P 2 S 5 (LPS) stands out due to its low Young's modulus (E = 18.5 GPa) [10] and its ability to be well densified by cold pressing. [11] Theoretically, the elasticity of LPS is beneficial for accommodating the stress caused by the volume change of the active material during cycling. However, All-solid-state batteries (SSBs) are considered as attractive options for next-generation energy storage owing to the favorable properties (unit transference number and thermal stabilities) of solid electrolytes. However, there are also serious concerns about mechanical deformation of solid electrolytes leading to the degradation of the battery performance. Therefore, understanding the mechanism underlying the electromechanical properties in SSBs is essentially important. Here, 3D and time-resolved measurements of an all-solid-state cell using synchrotron radiation X-ray tomographic microscopy are shown. The gradient of the electrochemical reaction and the morphological evolution in the composite layer can be clearly observed. Volume expansion/compression of the active material (Sn) is strongly oriented along the thickness of the electrode. While this results in significant deformation (cracking) in the solid electrolyte region, organized cracking patterns depending on the particle size and their arrangements is also found. This study based on operando visualization therefore opens the door toward rational design of particles and electrode morphology for all-solid-state batteries. BatteriesThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

No abstract

flask was heated under nitrogen for 2 h at 160-170 °C (oil bath temperature), allowed to cool, and refrigerated overnight. The product was collected by filtration, washed successively with DMF, ethanol, and ether, and dried in vacuo to give 0.14 g (47%) of a yellow powder, mp > 300 °C. The analytical sample was prepared by recrystallization from DMF: IR (KBr) 3440,3385,3340, 2220, 1700 (br), 1665,1635,1600 cm"1. The compound was too insoluble in Me2SO or TFA for determination of its NMR spectrum.