How to Solve the Safety Problem of High Capacity Lithium Battery

With the rapid development of wearable equipment, electric vehicles, etc., the "high-capacity" standard for batteries is also constantly improving. Lithium batteries with lithium metal as the negative electrode have 10 times the capacity potential of traditional lithium-ion batteries, but there are potential safety risks.

On the 28th, it was learned from Hunan University that the team of Jianghanqing of Arizona State University and the team of Rice University Tang Ming, together with the team of Duan Huigao of the school, had a research result on the "lithium dendrite" problem, which is expected to help solve such "high-energy" lithium batteries. Safety "trouble". This achievement was recently published in the top international energy journal Nature Energy.

Graphite is a negative electrode material for traditional lithium ion batteries with a storage capacity of 380 mAh/g. However, this is much lower than the theoretical capacity of lithium metal than 3860 mAh/g. Therefore, lithium metal is a more ideal negative electrode material for high-capacity batteries. However, batteries with lithium metal as the negative electrode in the early days will produce dendritic metal lithium during charging and discharging, IE, "lithium dendritic" problems. This may lead to a short circuit or even explosion in the battery, which is a potential safety hazard.

In order to solve the problem of the growth of lithium dendrites, various solutions are proposed. Including the addition of organic additives in electrolytes, or the use of solid electrolytes to inhibit dendritic production. Recently, the research team's findings on the problem of lithium dendrites are expected to help "disintegrate" the formation of lithium dendrites from a new perspective.

Jianghanqing said they found that the compressive stress was widespread during metal deposition. On the soft substrate prepared by the team, copper film was deposited as a collection fluid, and the electrode was assembled into a battery and charged under a microscope. It was found that after charging for a period of time, a one-dimensional fold structure suddenly appeared on the copper film. Through the instability of the copper film, the stress on the soft substrate was greatly released. It is proved that the pressure stress on the electrode surface can drive the growth of lithium dendrites. At the same time, they studied the deposition morphology of lithium metal on copper foil and soft matrix fluids, and proved that stress release can effectively prevent dendritic formation.

It is reported that the team also studied ways to use the soft substrate energy to release stress more effectively. They used sugar as a template to obtain a three-dimensional porous soft substrate. Compared with commercial copper foil and three-dimensional foam copper, it is found that it has better electrochemical performance.

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