Electroless Copper Metallization for Improving Li-Ion Batteries Performances

Electroless metallization, both autocatalytic and galvanic displacement, is a viable process to deposit copper on materials of interests for the production of electrodes in Li-ions batteries. In this work, examples of electroless copper deposition on lithium cobalt oxide (LiCoO2) and silicon particles for cathode and anode preparation respectively will be discussed, evaluating the improvement in the electrochemical behavior of the battery. Lithium cobalt oxide (LiCoO2) is the most widespread used active material in conventional cathodes for lithium-ion batteries. Its structural and electrochemical properties have been extensively studied [1-3]. The value of LiCoO2 charge capacity, 150 mA h g-1, is one of the reasons that prompted research in seeking for alternatives to be used at the positive electrode. Plenty of cathode materials have been studied, for example spinels [2,4] and LiFePO4 [2,5] amongst the others. Moreover, modification of lithium cobalt oxide properties has been achieved by coatings of the active material with different materials and with various techniques [6,7].

In this work, copper coating has been applied on LiCoO2 particles in order to allow the use of water as solvent in the manufacturing process of the cathodes for Li-ion batteries. The deposition was done with autocatalytic technique in a formaldehyde bath, through a two steps process: (i) Pd-activation of the particles and (ii) the growth of the coating on the particles with the reduction of Cu ions. The treatment allowed the deposition of a homogeneous copper layer on the particles. The electrodes manufactured with the coated powders of active material showed an increased electrical conductivity. Electrochemical characterization has been carried out to investigate the nature of the coating, and performances of the obtained cathodes have been evaluated by means of galvanostatic cycling in coin cells after the first 50 cycles at 0.33 C. The presence of copper on the particles of active material has shown its effectiveness under more severe cycling conditions. The coating allows using water as solvent in the preparation of the cathodes, leading to NMP-free manufacturing process of lithium-ion batteries. Electroless copper deposition was used also to coat silicon particles for anode preparation. Both autocatalytic deposition and galvanic displacement in fluoride containing solution have been tested. Silicon particles copper coated are characterized by better performances at the beginning of the cycling test; with cycling, lithiation/delithiation capacity for copper coated electrodes becomes comparable with the one obtained without copper.

Acknowledgements

With the contribution of the LIFE financial instrument of the European Community - LIFE12 ENV IT 000712   LIFE+ GLEE.

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