A ceramic solid-state electrolyte of lithium aluminum titanium phosphate with the composition of Li[Formula: see text]Al[Formula: see text]Ti[Formula: see text](PO[Formula: see text] (LATP) was synthesized by a sol–gel method using a pre-dissolved Ti-source. The annealed LATP powders were subsequently processed in a binder-free dry forming method and sintered under air for the pellet preparation. Phase purity, density, microstructure as well as ionic conductivity of the specimen were characterized. The highest density (2.77[Formula: see text][Formula: see text] with an ionic conductivity of [Formula: see text] (at 30[Formula: see text]C) was reached at a sintering temperature of 1100[Formula: see text]C. Conductivity of LATP ceramic electrolyte is believed to be significantly affected by both, the AlPO4 secondary phase content and the ceramic electrolyte microstructure. It has been found that with increasing sintering temperature, the secondary-phase content of AlPO4 increased. For sintering temperatures above 1000[Formula: see text]C, the secondary phase has only a minor impact, and the ionic conductivity is predominantly determined by the microstructure of the pellet, i.e. the correlation between density, porosity and particle size. In that respect, it has been demonstrated, that the conductivity increases with increasing particle size in this temperature range and density.

High interfacial resistance between solid electrolyte and electrode of ceramic all-solid-state batteries is a major reason for the reduced performance of these batteries. A solid-state battery using a monolithic all-phosphate concept based on screen printed thick LiTi(PO) anode and LiV(PO) cathode composite layers on a densely sintered LiAlTi(PO) solid electrolyte has been realized with competitive cycling performance. The choice of materials was primarily based on the (electro-)chemical and mechanical matching of the components instead of solely focusing on high-performance of individual components. Thus, the battery utilized a phosphate backbone in combination with tailored morphology of the electrode materials to ensure good interfacial matching for a durable mechanical stability. Moreover, the operating voltage range of the active materials matches with the intrinsic electrochemical window of the electrolyte which resulted in high electrochemical stability. A highly competitive discharge capacity of 63.5 mAh g at 0.39 C after 500 cycles, corresponding to 84% of the initial discharge capacity, was achieved. The analysis of interfacial charge transfer kinetics confirmed the structural and electrical properties of the electrodes and their interfaces with the electrolyte, as evidenced by the excellent cycling performance of the all-phosphate solid-state battery. These interfaces have been studied via impedance analysis with subsequent distribution of relaxation times analysis. Moreover, the prepared solid-state battery could be processed and operated in air atmosphere owing to the low oxygen sensitivity of the phosphate materials. The analysis of electrolyte/electrode interfaces after cycling demonstrates that the interfaces remained stable during cycling.

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High rate capability and long-term cycling spindle-like LiTi 2 (PO 4 ) 3 /C anode and needle-like Li 3 V 2 (PO 4 ) 3 cathode have been evaluated in half-cell, and combined to fabricate an advanced fast cyclable all phosphate lithium-ion battery. The electrode materials with well-defined morphology were prepared by a solvothermal reaction followed by annealing, delivering capacities of 115.0 and 118.1 mAh · g −1 at 25 • C over 200 cycles at 0.5 C, respectively. For the full cell assembly, no prelithiation process is needed for the selected electrode pair due to their mutually matched capacity and stoichiometric amount of lithium-ions. The fabricated full cell, with an output voltage of more than 1.5 V, inherits a superior rate capability and cycling performance of its electrodes. A discharge capacity of 36 mAh · g −1 at 30 C (about 30% of the initial discharge capacity at 0.1 C) and a capacity retention of ∼35% at 5 C over 1000 cycles has been achieved. Furthermore, one of the most important reasons for the capacity fading in the full cell during long-term cycling is found to be a decomposition and structural degradation of Lithium-ion batteries are widely used in portable electronics and are a promising energy storage system for electric vehicles because of their high energy density and long cycle life.1,2 However, current lithium-ion battery technologies are still far from satisfaction to meet the increasingly diverse range of applications. For instance, the use of lithium-ion cells in large scale applications, such as electric vehicles, demands high charge/discharge cycling performance and an inherent high thermal stability.3,4 Micro-lithium-ion batteries which can be applied to human body require in first instance the considerations of safety issue and cycling performance. 5,6 For the development of a novel type of lithium-ion battery like all-solid-state lithium-ion battery, one of the urgent needs to be addressed is to improve the ionic and electronic conductivity among the whole battery system. 7,8 Additionally, high rate performance and long cycle life are required for lithium-ion battery as stationary application for power management. To advance the battery technologies according the desired applications, it is important to explore the cathode and anode materials, and match them reasonably and to investigate their electrochemical performances. [10][11][12] have attracted much attention because more than two formula units of Li-ions can possibly intercalate/deintercalate into/from their host crystal structure during discharge/charge at a moderate working potential. On the basis of the crystal structure in these cathode materials, the use of phosphate polyanions (PO 4 ) 3− is considered as a potential alternative to oxide-based cathodes. The strong P−O bonds and the framework of (PO 4 ) 3− anions can guarantee both the dynamic and thermal stabilities required to fulfill the safety requisites in high-power applications.18 More than that, phosphate materials are also believed to be superior candidates of an...

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To improve the lifetime of lithium-ion batteries, a detailed understanding of the degradation mechanisms is essential. Nuclear magnetic resonance (NMR) is able to unravel the reversible as well as irreversible transient changes of composition, shape and morphology in a battery cell. Using a newly developed cylindrical battery container free of metallic components in combination with a numerically optimized saddle coil, in operando NMR investigations of battery cells over hundreds of charge/discharge cycles are presented. Alternating with NMR data acquisition, electrochemical impedance spectra (EIS) can be recorded, which enables correlative analysis of the two techniques. Long-run in operando NMR measurements on a Li metal vs. graphite cell reveal the formation and evolution of mossy and dendritic Li microstructures over a period of 1000 h, which illustrates the capabilities of NMR to identify dendrite mitigation strategies in cells operated under realistic conditions.

For an accurate characterization of transport and mobility processes in batteries using electrochemical impedance spectroscopy (EIS), a large frequency range of up to ten decades must be covered. It is experimentally demonstrated, for the first time, that the phase of the impedance measurements converges in the sub-millihertz range, which permits a reliable quantification of diffusion kinetics. To avoid a considerable change of the state of charge (SOC) of the battery and to mitigate the very long measurement times caused by standard EIS, a combination of EIS and time domain measurements, the time-domain supported electrochemical impedance spectroscopy (TD-EIS), is employed. To ensure an utmost comparability and reproducibility of the results with minimum influence of the cell fabrication, the method is demonstrated using three equivalent, industrially manufactured lithium-ion pouch cells at varying temperatures. The obtained impedance data were fitted by an electrical equivalent circuit battery model for an accurate estimate of charge transfer resistance and, in particular, also solid-state diffusion rate. Both processes follow an Arrhenius law, allowing the determination of activation energies with small variance. The obtained results are within the range of literature values measured for similar systems. The relevance of very low frequency impedance data for accurate fitting of mobility parameters in batteries is discussed.