Ni oh 2

Li-rich layered oxides were prepared by using Li₂CO₃, Ni(OH)₂, MnCO₃, and RuO₂ as precursors, which were purchased from Sigma Aldrich. Precursors at a stoichiometric ratio of Li: Ni: TM = 1.2:0.2:0.6 (TM = Mn, Ru) were first mixed on a Spex 8000 mill for 3 h, followed by a calcination process at a temperature of 950 °C for 15 h in air.

LNMO particles were synthesized via polyol method adopting a similar procedure as previously described elsewhere for the undoped LMO [45 (link)]. LiOH (Merck, Darmstadt, Germany, >98%), Ni(OH)₂ (Sigma-Aldrich, Steinheim, Germany, 99.2%) and electrolytic manganese oxide (EMD, grade HMR-AF, Tosoh, Tokyo, Japan, 92.5%) were selected as metal precursors. The Li:Mn and Mn:Ni precursor molar ratios were set as 2.12 and 2.77, respectively. As solvent and reducing agent, ethylene glycol (EG, Steinheim, Germany, >99.5%) was used. After the reaction, the acquired precipitates were recovered by centrifuging in 50 mL polystyrene tubes (Carl Roth, Karlsruhe, Germany) using a UniCen MR centrifuge (Herolab, Wiesloch, Germany) with 14,000 rpm for 30 min at 20 °C. They were washed twice with acetone and centrifuged with 5000 rpm for 5 min. Afterwards, the as-synthesized LNMO powders were dried under vacuum at room temperature for 3 h, ball milled and calcined at 250 °C and 800 °C in air. For purposes of comparison, LMO particles were also synthesized according to Yang et al. [45 (link)], ball milled and calcined at 250 °C to remove the organic residual and then at 800 °C for the formation of the spinel phase. A more detailed description of the sample preparation can be found elsewhere [45 (link)].

Cathodes are prepared as follows: 700 mg of Ni(OH)₂ (Sigma-Aldrich), 200 mg of Acetylene black, 100 mg of polyvinylidene difuluoride (Kynar HSV900) and 10 ml of N-methyl-2-pyrrolidone (Sigma-Aldrich) were mixed and stirred for 12 h at room temperature. The obtained slurry was dip coated on current collector of Ni foam (2 mm thick) and dried at vacuum oven 80 °C. Dried Ni foam was pressed in to 0.1 mm to be used as cathode. Approximately 4.8 mg commercial Ni(OH)₂ is loaded on the prepared cathode. Carbon coater (EMS150R ES) was used for sputtering the amorphous carbon nano layer. Carbon fibres were used as the evaporation target. The evaporation chamber was pumped down to 5 × 10⁻² mbar before an out gassing current of 30 A was passed through the carbon fibres. After out-gas recovery, a pulse current was passed through the fibre to allow flash evaporation of carbon. The pulse current was set to 60 A for 20 s, with a 10-s interval between pulses. All the procedure is the same as that in ref. 18 (link). A mask was used to coat the carbon layer on only the edge of Cu substrate. The edge-protected Cu substrate was then glued to PP film by Polyvinyl butyral (Santa Cruz Biotechnology).