Lithiated metallic anodes (LixSn1-x) with internal Ga-rich liquid matrix for rechargeable lithium ion batteries

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The new generation of lithium ion batteries with distinctly higher charge densities and cycling stabilities than exhibited by todays state of the art cells is predominantly hindered by the lack of suitable reversible negative electrode materials. A new approach compared to the use of commercial carbon negative electrodes has been established rather early by the use of intermetallic anode materials based on e.g., Sb, Si and Sn. While these materials express significant higher charge capacities they suffer from large volume swings during electrochemical cycling which cause disintegration of the electrode material and hence loss of electrical contacts between active particles. High attention was given to a recently published study where a regular self-healing effect of pure Ga as anode material was demonstrated which can simultaneously heal the expansion induced cracks. The motivation of the current proposal is to design the first heterogeneous Sn based anode material with a low melting Ga-rich phase as an internal matrix. Apart from usually time-consuming and expensive evaluations of prototype electrode materials, strategies will be employed to directly correlate thermochemical properties, equilibrium diagrams and electrochemistry by using the CALPHAD method which is up to now the most advanced method for thermodynamic modeling and optimization of complex heterogeneous systems. A careful design of GaxSn1-x anode materials will be supplemented by a simultaneous improvement of the thermodynamic description of the Ga-Li-Sn system based on suitable key experiments. In focus will be the accurate description of non-stoichiometric compounds based on well-defined sublattice models according to crystallographical available information. The reliable description of defect mechanisms and site occupations within the crystal lattice of the actual insertion materials will improve also the understanding of the lithiation process in other intermetallic materials and may inspire the design of new reaction mechanisms for Li ion batteries. Throughout the work, proper anode materials with well-defined macroscopic properties will be designed and exact predictions of the lithiation mechanism will be made. Electrochemical cycling tests of GaxSn1-x electrodes will be used for verifying previous predictions from the calculations as well as provide information on modeling improvements through an iterative data generation and evaluation process. The proposed approach will allow the extension to any intermetallic anode material of interest to achieve a closer connection between basic materials research and advanced materials application.