Holes are made in a Si negative electrode by laser processing after the electrode is formed on a stainless material. When light is applied to the back side of the electrode, it passes through the electrode.

Wired Co Ltd developed a technology to continuously make many minute holes in the electrode material of a lithium-ion (Li-ion) rechargeable battery by using a laser device.

With the electrode material, the pre-doping of Li ions, which is indispensable for increasing the capacity of next-generation Li-ion rechargeable batteries, becomes easier. And it enables to increase the use of (1) electrode materials whose irreversible capacities are large and (2) high-capacity positive-electrode materials that are not lithium compounds, according to Wired.

New materials are being developed for next-generation high-capacity Li-ion rechargeable batteries. On the other hand, compound with Li is formed on, for example, electrodes at the time of initial charge, decreasing the number of Li ions used for charging/discharging and making it impossible to increase capacity.

As a solution to this problem, the pre-doping technology that places Li foil in a cell in advance and externally short-circuits the negative electrode and Li foil to supply Li ions is drawing attention.

The structure of a cell that uses a laser-processed electrode and can be pre-doped. Pre-doping enables to supply Li, which is in short supply in the cell, and increase capacity.

Wired aims to apply its laser processing technology to silicon (Si) negative electrodes, which are expected to be widely used as high-capacity negative-electrode materials. The theoretical capacity of Si negative electrode is 4,200mAh/g, which is more than 10 times higher than that of conventional graphite negative electrode. However, without pre-doping, the initial charge/discharge efficiency of Si negative electrode becomes about 80%, lowering discharge capacity.

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