The gas evolution in LFP/graphite and LFMP/graphite cells during the formation has been analyzed via neutron imaging (NI). The results show that in LFMP/graphite cells approximately 30% more gas is generated in comparison to LFP/graphite and stronger gas evolution is associated with the presence of Mn. For the LFP/graphite cell two different linear phases in gas evolution rate can be detected while LFMP/graphite cells reveal an additional phase. In both full-cells a distinct relation between gas evolution and electrode potentials has been determined. Additional neutron induced Prompt Gamma Activation Analysis (PGAA) measurements were carried out in order to correlate long-term Mn dissolution and capacity retention. Long-term cycling showed higher capacity retention for the LFMP/graphite cells. The results of PGAA prove that Mn dissolution decreases rapidly with increased cycle number and the Mn dissolution rate of LFMP is far below values observed for oxide-type cathode materials. Long-term cycling showed that the negative effects of higher irreversible capacity loss in the formation step and more gas evolution of LFMP/graphite cells in comparison to LFP/graphite cells is compensated after several cycles due to higher capacity retention. Due to their high energy density and operating voltage lithiumion batteries are a key technology for mobile applications such as communication devices and electric vehicles.1-3 But also stationary energy storage systems are increasingly developed under usage of lithium-ion technology. Those stationary storage systems range from small (e. g. home storage for photovoltaic plants) to large scale applications (grid stabilization). [4][5][6] Especially in cases of high capital expenditures, consumers and operators expect a long battery lifetime in terms of capacity and charge and discharge characteristics.Applications like home energy storage require high operational safety standards. These requirements are met by the cathode active material LiFePO 4 (LFP), which has first been described in 1997. Phospho-olivines such as LFP provide good operational characteristics in terms of thermal runaways and are furthermore environmentally friendly and cost-efficient. The dissolution of Mn from LFMP as such has recently been investigated and a strong correlation between dissolved Mn and traces of H 2 O contamination in the electrolyte has been stated. It has also been found that in case of LFMP there is no selective dissolution of Mn since Fe is dissolved as well and the Mn/Fe ratio in the electrolyte and the active material is equal. 18Another study has shown that transition metal dissolution also occurs in oxide-type active materials such as layered Nickel-ManganeseCobalt oxide based active materials (NMC). 19 In case of NMC all z E-mail: benjamin.starke@haw-landshut.de present transition metals Ni, Mn and Co dissolve in the electrolyte and migrate to the anodic graphite. But while Ni and Co remain in the oxidation state +II, Mn is reduced to Mn 0 and subsequently reoxidized to Mn 2+ under co...

LiFePO 4 (LFP) primary particles and secondary agglomerates have been processed into water-and solvent-based cathodes. By means of neutron and X-ray diffraction it was found that no structural changes of LiFePO 4 occurred upon water-and solvent-based slurry preparation. Electrochemical characterization was carried out with full-cells and a distinct influence of particle morphology was observable. Water-based processing of primary particles leads to deficits in electrochemical performance while secondary agglomerates are non-sensitive to water during processing. In the presence of water, high mechanical stress during slurry preparation causes a partial detachment of carbon coating. However, this effect is negligible for secondary agglomerates since only surface particles are exposed to mechanical stress. Due to longer diffusion paths and the fact that secondary agglomerates represent a micro-heterogeneity in the cathode, the C-rate capability of secondary agglomerates is slightly lower than that of primary particles. This paper demonstrates that for any high energy application with moderate C-rates, secondary agglomerates hold a great potential for environmentally friendly and cost-efficient water-based cathode production.

LiFeMnPO 4 secondary agglomerates have been aged under different temperature and moisture conditions. The aged and pristine powder samples were then processed to water-and solvent-based cathodes. Structural studies by means of neutron and X-ray diffraction revealed that neither ageing nor water-based processing significantly modified the crystal structure of LiFeMnPO 4 secondary agglomerates. Electrochemical characterization was carried out with full-cells. It was found that long-term cycling is similar independent of the solvent used for slurry preparation. Full-cells assembled with water-based cathodes show a better C-rate capability due to a more homogeneous distribution of cathode constituents compared to solvent-based ones. In no case was any negative effect of initial active material ageing on the electrochemical performance found. During ageing and processing, LiFeMnPO 4 is effectively protected by carbon coating and water can be completely removed by drying since it is only reversibly bound. This contribution shows that LiFeMnPO 4 secondary agglomerates allow simplified active material handling and have a high potential for sustainable water-based electrode manufacturing.