A Si-based anode with improved performance can be achieved using high-energy ball-milling as a cheap and easy process to produce Si powders prepared from a coarse-grained material. Ball-milled powders present all the advantages of nanometric Si powders, but not the drawbacks. Milled powders are nanostructured with micrometric agglomerates (median size ∼10 μm), made of submicrometric cold-welded particles with a crystallite size of ∼10 nm. The micrometric particle size provides handling and non-toxicity advantages compared to nanometric powders, as well as four times higher tap density. The nanostructuration is assumed to provide a shortened Li⁺ diffusion path, a fast Li⁺ diffusion path along grain boundaries and a smoother phase transition upon cycling. Compared to non-milled 1–5 μm powders, the improved performance of nanostructured milled Si powders is linked to a strong lowering of particle disconnection at each charge, while the irreversibility due to SEI formation remains unchanged. An electrode prepared in acidic conditions with the CMC binder achieves 600 cycles at more than 1170 mA h per gram of the milled Si-based electrode, in an electrolyte containing FEC/VC SEI-forming additives, with a coulombic efficiency above 99%, compared to less than 100 cycles at the same capacity for an electrode containing nanometric Si powder.

A polycrystalline copper electrode was activated by creating a nanostructured and highly electrocatalytic surface through an appropriate electrochemical treatment in <mml:math display="inline"><mml:mrow><mml:mn>1</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi mathvariant="normal">M</mml:mi></mml:mrow></mml:math>1M NaOH. It was demonstrated that a thick layer <mml:math display="inline"><mml:mrow><mml:mo>(</mml:mo><mml:mo>∼</mml:mo><mml:mn>2</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>μ</mml:mi><mml:mi mathvariant="normal">m</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:math>(∼2μm) of <mml:math display="inline"><mml:mrow><mml:mi mathvariant="normal">Cu</mml:mi><mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:mi mathvariant="normal">O</mml:mi><mml:mi mathvariant="normal">H</mml:mi><mml:mo>)</mml:mo></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Cu(OH)2 nanoneedles can be formed on copper substrate after <mml:math display="inline"><mml:mrow><mml:mn>3000</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mtext>cycles</mml:mtext></mml:mrow></mml:math>3000cycles (scan rate <mml:math display="inline"><mml:mrow><mml:mn>10</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi mathvariant="normal">V</mml:mi><mml:mspace width="0.3em"></mml:mspace><mml:msup><mml:mi mathvariant="normal">s</mml:mi><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>10Vs−1 ) between <mml:math display="inline"><mml:mrow><mml:mo>−</mml:mo><mml:mn>1650</mml:mn></mml:mrow></mml:math>−1650 and <mml:math display="inline"><mml:mrow><mml:mn>1000</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mV</mml:mi></mml:mrow></mml:math>1000mV vs <mml:math display="inline"><mml:mrow><mml:mi mathvariant="normal">Hg</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">Hg</mml:mi><mml:mi mathvariant="normal">O</mml:mi></mml:mrow></mml:math>Hg∕HgO or by anodization for <mml:math display="inline"><mml:mrow><mml:mn>15</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>min</mml:mi></mml:mrow></mml:math>15min at <mml:math display="inline"><mml:mrow><mml:mo>−</mml:mo><mml:mn>100</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mV</mml:mi></mml:mrow></mml:math>−100mV . Energy dispersive X-ray analysis, X-ray diffraction, X-ray photoelectron spectroscopy, and in situ Raman spectroscopy analyses revealed that the conversion of orthorhombic <mml:math display="inline"><mml:mrow><mml:mi mathvariant="normal">Cu</mml:mi><mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:mi mathvariant="normal">O</mml:mi><mml:mi mathvariant="normal">H</mml:mi><mml:mo>)</mml:mo></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Cu(OH)2 to face-centered-cubic Cu is completed after <mml:math display="inline"><mml:mrow><mml:mn>20</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mtext>cycles</mml:mtext></mml:mrow></mml:math>20cycles between <mml:math display="inline"><mml:mrow><mml:mo>−</mml:mo><mml:mn>450</mml:mn></mml:mrow></mml:math>−450 and <mml:math display="inline"><mml:mrow><mml:mo>−</mml:mo><mml:mn>1650</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mV</mml:mi></mml:mrow></mml:math>−1650mV at <mml:math display="inline"><mml:mrow><mml:mn>20</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mV</mml:mi><mml:mspace width="0.3em"></mml:mspace><mml:msup><mml:mi mathvariant="normal">s</mml:mi><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>20mVs−1 . However, copper obtained from the reduction of the thickest <mml:math display="inline"><mml:mrow><mml:mi mathvariant="normal">Cu</mml:mi><mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:mi mathvariant="normal">O</mml:mi><mml:mi mathvariant="normal">H</mml:mi><mml:mo>)</mml:mo></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Cu(OH)2 nanoneedle films formed by a repetitive fast cycling or by anodization at <mml:math display="inline"><mml:mrow><mml:mo>−</mml:mo><mml:mn>100</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mV</mml:mi></mml:mrow></mml:math>−100mV appeared as nanowires, whereas the electrode anodized at 0 or <mml:math display="inline"><mml:mrow><mml:mn>700</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mV</mml:mi></mml:mrow></mml:math>700mV recovered a quasi-smooth original copper surface. The presence of high-energy sites on these Cu nanostructures was highlighted by cyclic voltammetry in the pseudo-capacitive potential region, where premonolayer oxidation was observed with an unusually high magnitude at unusually low potentials. As a result, a remarkable improvement of the electrocatalytic activity of the activated Cu electrodes for the nitrate electroreduction was observed.