RRP 4: An increased energy density lithium battery

Person Responsible: Marjan Bele, PhD (National Institute of Chemistry)

The main goal of this project is to synthesise and use new lithium electrode materials with a significantly higher energy density than that of the currently available materials. This will enable us to store significantly more energy in a mass unit or battery volume than in existing batteries.

We will attempt to increase the energy density in two ways: by synthesising cathode materials with significantly higher capacities than the existing cathode materials, and by synthesising cathode materials with a significantly higher potential.

A) Materials with a higher capacity: The existing cathode materials can store a maximum of 1 mol of lithium per mol of active compound. Recently, we were the first in the world to synthesise a new siliceous material (Li2MnSiO4) that could theoretically store and release 2 mol of lithium per 1 mol of compound. This theoretical goal has not yet been achieved in practice. The project aims to optimise the structural and microstructural properties of new siliceous materials so that they will be able to exchange significantly more than 1 mol of lithium per mol of compound – reversibly.

B) Materials with a higher potential: The currently most popular cathode material is LiFePO4. This is a very stable and relatively safe material with a solid capacity (160 mAh-1). Its biggest weakness is its relatively low potential (3.4 V compared to metal lithium). There is a considerable amount of literature on how replacing iron (Fe) with manganese (Mn) increases the potential by 0.7 to 0.9 V. The problem, however, is that manganese analogue is very poorly conductive, making lithium extraction/insertion extremely difficult.

The solution to the problem and the goal of this project is to prepare LiMnPO4 in the form of very small particles (10-20 nm) and to bind them electrochemically using a suitable conductor (carbon nanofilm etc.). This would drastically increase the speed of lithium exchange and give us an excellent new material with a 25% higher energy density than LiFePO4.

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