The pre-doping of Li+ ions (pre-lithiation) in graphite anodes, which is needed to improve the initial charging/discharging efficiency of lithium ion batteries, was examined from the viewpoints of lithium metal deposition, surface electrolyte interface (SEI) formation and electrode potential changes in the cathode during the pre-lithiation. Using a cell composed of pre-laminated, through-holed anodes and cathodes, the anodes were pre-lithiated with the perpendicular pre-doping method, as explained in this work, which can effectively enhance the pre-lithiation process in laminated cells. In the pre-lithiation system, Li deposition was not observed on the anode surfaces during pre-lithiation, and the thickness of the SEI layers formed on the anodes did not increase. Moreover, the SEI layer has the same composition as that formed by the electrochemical lithiation (charging) process, even when the pre-lithiation of the anodes is accelerated by through-holes formed on the anode and cathode electrodes. In addition, the electrode potential of cathodes inserted between pre-lithiated anodes does not change during the pre-lithiation process, and the capacity of the cathodes does not degrade upon pre-lithiation. The perpendicular pre-doping method examined in this study is found to be applicable to the production process of lithium ion batteries with high charging/discharging efficiency. WIRED Co., Ltd.

A process for fabricating porous graphite electrodes having an average pore diameter of 21 μm and an open area of 1% was developed with a system constructed from a pico-second pulse laser and a polygon mirror. The fabricated porous graphite electrodes were used to evaluate the porous design on the graphite electrodes for exhibiting a higher Li+ pre-doping reaction (pre-lithiation) rate with cells in which graphite electrodes were laminated with separators and the laminated graphite electrodes opposite to a Li metal foil through a separator. The results in this study indicate that lithiation proceeds stepwise from the first electrode close to the Li foil to more distant electrodes. The transfer of Li+ ions controlled the lithiation because lithiation did not occur in areas of the electrodes that did not contain pores. In addition, the porous electrodes exhibited a much higher rate of lithiation when compared with electrodes that were prepared by coating a graphite layer on porous current collectors.　　WIRED Co., Ltd.