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The recycling of cathode materials for spent NCM has always been a major concern for the energy industry. However, among the current processing methods, the general leaching efficiency of Li is between 85% and 93%, with much room for improvement. The recovery of Ni, Co and Mn requires a high cost of secondary purification. In this study, to recycle the NCM cathode material, a route of sulphated reduction roasting – selective Li water leaching – efficiency acid leaching of Ni, Co, Mn – extraction separation – crystallisation was adopted. The results showed that after roasting (a temperature of 800 °C, a reaction time of 90 min, a carbon content of 26%, and a sulphuric acid addition of nH2SO4:nLi = 0.85), Li water leaching efficiency was 98.6%, followed by acid leaching of Ni, Co and Mn at around 99%. Mn, Co were extracted with Di-(2-ethylhexyl) phosphoric acid and 2-Ethylhexyl phosphonic acid mono-2-ethylhexyl ester respectively to obtain Ni, Co, Mn solutions, which eventually were crystallized for manganese sulphate, cobalt sulphate, lithium carbonate and nickel sulphate products, with high purity of 99.40%, 98.95%, 99.10%, and 99.95%. The results of this study improved the leaching efficiency of Li and were closely linked to the actual industrial preparation of Ni, Co and Mn sulphates, providing a feasible and promising basis for spent NCM cathode materials industrial recovery.

This paper proposes a joint linear precoding and power allocation design scheme for multiuser multiple-input multiple-out (MU-MIMO) cognitive radio (CR) systems, where secondary users share the same spectrum with one primary user. The interference power constraint required by the primary user and the multiuser interference generated by secondary users impose negative influence on each secondary user. As a result, it is difficult for secondary users to achieve the ideal information rate. In order to solve the above problem, we respectively adopt Channel Inversion (CI) and Block Diagonalization (BD) for precoding matrices which are set at the transmitter of each secondary user, and then make the system reach a steady state by power allocation. In fact, perfect CSI cannot exist in wireless systems. Therefore, it’s necessary to consider imperfect CSI. Simulation results show BD gains a higher rate for secondary users, but imperfect CSI causes less loss to CI.