Li-based batteries are known for their high capacity, relatively high voltage, and lower mass density compared to other battery systems. This makes Li-ion batteries ideal for a range of products, such as electric car batteries, smartphones, and other rechargeable systems. However, the structure of battery cells and the materials used in their construction tend to make commercial Li-ion batteries more expensive than equivalent batteries with aqueous electrolytes. As such, disposable alkaline batteries and zinc/air batteries have dominated the small battery market, particularly for consumer products.
Rechargeable Li batteries use solid Li as the anode, or they use a carbon-based material (e.g., graphite) or another alloy that permits intercalation of Li+ in the solid electrolyte interphase (SEI) layer. Due to dendritic growth on the anode in Li batteries, which decreases lifetime and leads to thermal failure, this latter range of anode materials has come to form the basis of Li-ion batteries. Graphite is the current best-in-class anode material used in Liionbatteries as large concentration of Li+ can adsorb/desorb from carbon (C:Li = 6:1) during charging/discharging. Although one is hard pressed to find consumer, industrial, and military products that don’t contain Li-ion batteries, there is always a motivation to build a better battery. The goals would be to increase capacity and charge/discharge rates without increasing thermal losses during operation. There are still challenges inhibiting these improvements in Li-ion batteries:
ANODE RESISTANCE:
Reducing the terminal resistance of graphite anodes will reduce losses during charging/ discharging. This will then help prevent thermal failure and help extend battery lifetimes.
CAPACITY LIMITATIONS:
Although Li-ion batteries are known for their high capacity, it is always desirable
to increase the capacity in order to increase time between charging sessions.
OPERATION AT LOW TEMPERATURES:
Conventional Li-ion batteries with graphite anodes exhibit reduced discharge rate at low temperatures.
HIGH COST:
Any improvement in Li-ion battery materials should hold constant or decrease the overall cost per mAh of capacity to ensure broader commercialization.
Because of these challenges in increasing capacity and charge/ discharge rate, researchers have extensively investigated new materials for rechargeable batteries. There have been some interesting successes, but new materials often require changing the Li-ion battery chemistry. This in turn creates safety risks that need to be addressed during design and manufacturing in order to comply with safety regulations. This then makes companies liable for failed products and creates new barriers to commercialization.
Because it is desirable to improve the performance metrics mentioned above without changing the battery chemistry, there has been a considerable focus on the use of graphitic materials, carbon nanotubes, graphene, carbon black, activated carbon, and fullerene-like materials as anodes in Li-ion batteries. Advanced carbon-based materials with unique morphology can provide a solution to these challenges without changing the chemistry of Li-ion batteries.
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