Wednesday, February 1, 2023

This new technology boosts battery capacity by using silicon and a solid electrolyte

To improve the efficiency of lithium batteries, researchers have been working to improve their core components, working on the electrode or electrolyte that separates them (the lithium-based medium that conducts ions between the anode and cathode). transport allows). Thus, many studies focus on trying convert liquid electrolyte to solid or to modify cathode chemistry, Finally, as in the case of this new study, the work has been based on Modify the anode to avoid parasitic reactions that reduce efficiency,

Researched by the team of zhengwen fu, study co-author and electrochemist at Fudan University’s Laboratory of Molecular Catalysis and Innovative Materials. In an article describing the process, published in the journal Nano Research, one is explained New Anode Preparation Technique based on mixed content silicon-monoxide-carbon, Preliminary results show increased battery efficiency without the appearance of unwanted side reactions.

Prelithician Anodes Battery-Interior 2
Schematic illustration of the anode structure after cyclization of a LiCPON solid electrolyte battery and an anode made of carbon monoxide and silicon.

lithium battery anode

Until the 1990s, battery manufacturers used coking coal To make the structure of the battery anode (the negative terminal through which electric current enters). However, this material began to be replaced by leadA form of carbon, due to the long-term stability it provides over many charge and discharge cycles.

But, to further improve the performance of lithium-ion batteries, battery manufacturers are looking for alternatives to the anode. Due to a high specific capacity (discharge rate) and its abundance in the Earth’s crust, the most suitable materials are silicon-based compounds. especially, silicon monoxide The next generation of lithium-ion batteries has shown great promise.

The downside is that this material itself also has a number of disadvantages. among them is his low conductivity And its quantity changes during charge and discharge cycles. These variations of up to 300% result in destruction and segregation of the anode material, leading to a fundamental reduction in performance.

“The solution is to combine silicon monoxide with carbon into a composite material, which is a kind of mix between existing graphite anode materials and next-generation silicon-based anodes,” says Zhengwen Fu. “The compound offers the best of both worlds. But here, too, there are many hurdles to overcome.”

Carbon provides high electrical conductivity and structural stability. It also experiences a small amount of expansion during cycling. Its flexibility and ability as a lubricant act to inhibit the volume expansion of silicone. In general, this composite anode offers good capacitance and high cycling performance.

But all these advantages are not untouched by others. DrawbacksWhat do silicon-monoxide-carbon anodes suffer from? coulombic efficiency (the ratio of the total electric charge put into the battery to the total charge taken out of it) is relatively small. Although there is always less taken out than put in, the goal is to keep these inevitable losses to a minimum.

Prelithian Anodes Battery-Interior1
Research so far has used rechargeable button-cell batteries and will continue to work to demonstrate their feasibility on a larger scale.


During the first cycles of a prototype lithium-ion battery with an anode made of this new material, some of the lithium reacted irreversibly with the compound. The result is a series of products that form a layer between the anode surface and the solid electrolytic interface (SEI). This parasitic ‘lithiation’ process results in loss of active lithium and a decrease in Coulombic efficiency.

Other researchers have developed their own pre-lithiation techniques using pure lithium metal, a modified lithium metal, or a compound containing lithium. In all these cases there are limitations: lithium-containing compounds release a gas during the cycle after lithiation, which reduces the performance of the anode and the energy density of the battery as a whole.

To overcome these shortcomings, the researchers developed A new technique of ‘pre-litigation’ Which stores excess lithium in the battery in advance and compensates for the lithium consumed by parasitic reactions during the battery cycle.

The new process, which the researchers have dubbed ‘solid-state lithium corrosion’, eliminates all these problems. replace liquid electrolyte a solid electrolyte Carbon-incorporated lithium phosphorus oxynitride compound (LiCPON). In this way, not only are unwanted side reactions associated with lithium metal avoided, but a better interface is created between the anode and the electrolyte.

During the investigation, the team was able to verify whether their pre-corrosion was working via the solid-state lithiation process three different ways To observe electrochemical reactions in real time: optical imaging, electron microscopy and X-ray diffraction. Technique increased the efficiency of the anode 83% cases on prelithiation electrodes with liquid electrolyte.

tested in concept button cell batteryFor the research and development of small scale, laboratory batteries. The research team will now move on to the next step to see whether the process is maintained in industrial-sized batteries.

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