Cheap High Performance Li-ion Batteries

Calendar October 20, 2022 | Posted by admin

Li-ion batteries (LIBs) are one of the most used batteries that support modern ITC society, including smartphones and EVs. LIBs are repeatedly charged and discharged by Li-ions passing back and forth between the positive and negative electrodes, with the Li-ion electrolyte acting as a passageway for the ions.

Normally, organic electrolytes such as liquid ethylene carbonate (EC) and their gels have been used as the Li-ion electrolyte due to their voltage resistance and ionic conductivity. However, as liquids and gels are flammable, a switch to safer polymeric solid electrolytes is preferable.

Polymeric solid electrolytes such as polyethylene glycol (PEG) have been proposed as impact-resistant Li-ion electrolytes. However, PEG-based polymer electrolytes crystallize near room temperature, resulting in a significant drop in Li-ion conductivity to around 10-6 S/cm at room temperature. To solve this problem, a research group has invented a new type of polymeric solid electrolyte by combining a porous polymer membrane with several micron pores and a photo-cross-linkable polyethylene glycol PEG-based polymer electrolyte.

This polymeric solid electrolyte not only shows high performance as an electrolyte but is also expected to be effective in deterring the formation of Li dendrites (dendritic crystals), which can cause ignition, due to the inclusion of a porous membrane. Through the realization of safe, high-performance LIBs, this achievement will contribute to the realization of a sustainable energy supply, which is the seventh goal of the SDGs.

Source: https://www.tohoku.ac.jp/

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How To Extend The Charge-to-charge Life of Phones And Electric Cars By 40 %

Calendar February 22, 2019 | Posted by admin

The need to store energy for portable devices, vehicles and housing is ever increasing.The transformation from fossil fuels to renewable energy sources need to be hastened to decrease greenhouse gases and limit global warming. The utilization of wind and solar power requires effective storage system to ensure continuous energy supply as a part of smart grid. Li-ion batteries are considered to be the best route for many advanced storage applications related to the clean electricity due to their high energy density.

The latest lithium-ion batteries on the market are likely to extend the charge-to-charge life of phones and electric cars by as much as 40 percent. This leap forward, which comes after more than a decade of incremental improvements, is happening because developers replaced the battery’s graphite anode with one made from silicon. Research from Drexel University and Trinity College in Ireland now suggests that an even greater improvement could be in line if the silicon is fortified with a special type of material called MXene.

Regarding the present Li-ion batteries, one of the limiting factors in their performance is the anode material that most commonly is graphite. Silicon is a promising material for Li-ion battery anodes: By using silicon instead of graphite, the energy density of a battery cell ccould be increased by 30 %. To achieve this, several obstacles have to be overcome: First, silicon experiences a volume expansion of 300 % when lithiated. During discharging, the particles tend to fracture and lose contact. Secondly, the volume expansion prevents the formation of a stable electrode-electrolyte interface resulting in a continuous decomposition of the electrolyte. These two reasons are main causes for the limited use of silicon in commercial batteries.

The image shows PSi microparticles connected to each other with CNTs to improve the conductivity of the material

Both of the above mentioned problems with silicon material can be avoided by designing optimal porous structures of mesoporous silicon (PSi). Porosity of PSi needs to be high enough for the material to be able to withstand the volume expansion but also low enough so that the volumetric capacity/energy density is still better than for graphite anodes.

Source: https://www.nature.com/

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