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The study of nanostructured bulk and thin film LiFePO4 cathode materials for lithium-ion batteries
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MSc. Gints Kucinskis (ISSP UL)

In this work LiFePO4 lithium ion battery cathode material and its thin films have been studied. The possibilities of improving electrochemical properties and rate capability of LiFePO4 were analysed by optimizing the synthesis conditions and experimenting with reduced graphene oxide electron-conducting additive. LiFePO4 thin films were obtained, their structure, morphology and electrochemical properties were analysed. The model of sequential LiFePO4 particle charge and discharge was analysed and improved in context of the LiFePO4 bulk material and thin films. The results give extensive understanding of lithium insertion and de-insertion processes taking place in LiFePO4 cathode and demonstrates pre-requisites necessary for improving the rate capability of LiFePO4.

Proposed theses to be defended:

1. Anchoring LiFePO4 particles on a reduced graphene sheets is the most effective way of improving LiFePO4 rate capability with the help of reduced graphene oxide and one of the most efficient methods of improving LiFePO4 rate capability overall.

2. The efficient chemical lithium diffusion coefficient and its lithium concentration dependence is similar in both LiFePO4 bulk material and thin films, therefore the use of electron-conducting additives is not necessary in LiFePO4 thin films.

3. Lithium insertion and de-insertion in LiFePO4 bulk and thin film electrodes takes place sequentially (particle by particle). Considerable part of LiFePO4 grains in thin film electrode lithiates and delithiates via single phase mode.