Why would anyone want to drive a car that takes more than a minute to charge? However, imagine electric vehicles charging incredibly quickly and having long driving ranges, or a smartphone charging in less than a minute. While this may seem impossible, advancements in graphene batteries are making these possibilities a reality.
The degradation of lithium-ion batteries
Lithium-ion batteries are widely recognized as a promising alternative for energy storage applications due to their high energy density. These batteries power our computers, smartphones, and even cars. One remaining issue with lithium-ion batteries is safety. The liquid inside a lithium-ion battery is highly flammable. Any damage to the outer layer of the battery can cause a short circuit, leading to fires and explosions. For example, in 2016, a sudden explosion of a smartphone resulted in first-degree burns to several users worldwide. In recent years, lithium-ion batteries used in electric vehicles have gained widespread adoption of cooling systems. However, these cooling systems take up significant space that could be used for energy storage. Another issue with lithium-ion batteries is recyclability. Most components in lithium-ion batteries are not biocompatible, making the recycling process very expensive. Finally, the batteries have low power density. Take smartphones, for example: due to their high energy density, the battery can last for most of the day; to charge the device, it must be connected to another power source for an hour or more.
The Promise of Graphene
Graphene, a single-atom-thick sheet of carbon atoms with a relative surface area of 2.630 m²/g, exhibits excellent charge storage properties and shows almost no degradation during long-term cycling. The bonds in graphene give it a tensile strength more than four times that of steel, while also making it ultra-transparent, flexible, and an excellent electrical and thermal conductor. These properties make graphene suitable not only for batteries but also for supercapacitors. However, graphene supercapacitors store less energy than batteries, although they can be fully charged in minutes. Therefore, to overcome the low energy density of graphene supercapacitors, scientists have begun to study the coupling of supercapacitors and batteries as a hybrid energy storage system.
Graphene-aluminum hybrid battery
Researchers at the University of Queensland in Australia, in collaboration with Graphene Manufacturing Group (GMG), have developed a graphene-based hybrid battery prototype. This battery uses graphene and aluminum as electrode materials and is commonly referred to as a graphene-aluminum battery. The battery boasts an energy density of 150-160 Wh/kg and can be rapidly charged in 1-5 minutes. Furthermore, graphene-aluminum-ion batteries offer significant advantages in battery safety, recyclability, and longer battery life (over 2000 cycles) with minimal performance degradation. According to the latest information, GMG has announced that it has produced graphene-aluminum-ion batteries in pouch form for use in smartphones, tablets, laptops, and more. GMG states that the theoretical energy limit of these batteries is approximately 1050 Wh/kg. Therefore, with further development, we can soon expect graphene batteries to surpass the energy output of commercially available batteries.
Graphene-enhanced lithium-sulfur batteries
A watershed moment in the development of graphene hybrid batteries came in late 2021 when California-based Lyten announced the development of a graphene battery for electric vehicles with three times the energy density of conventional lithium-ion batteries. These batteries are lithium-sulfur (Li-S) batteries, long touted as the next generation of rechargeable batteries. However, a challenge for Li-S batteries in practical applications is the formation of soluble polysulfides during discharge cycles. These intermediates diffuse between the anode and cathode, causing internal short circuits. This phenomenon, commonly known as the shuttle effect, is the cause of the low efficiency and rapid capacity decay of Li-S batteries. Lyten overcame this problem by incorporating a 3D graphene film into the sulfur cathode, which acts as an effective separator and reduces the rate of capacity decay during cycles. The product, named LytCell EV, reportedly offers an energy density of 900 Wh/kg. Tests clearly showed that the LytCell prototype could sustain more than 1,400 charge-discharge cycles.
Graphene-enhanced polymer batteries
PolyJoule, a spin-off from MIT, recently announced a new battery technology for high-power data center backup and grid applications. The device is a dual-electrode electrochemical battery featuring a carbon-graphene blend and a conductive polymer. The battery can release up to 1 MW of energy in 10 seconds and recharge in 5 minutes. It operates from 158 V to 972 V, can operate continuously over a temperature range of -40 °C to 50 °C, and exhibits minimal capacity loss.
Graphene non-flammable lithium batteries
When lithium-ion batteries short-circuit, they can catch fire, raising concerns about their use in consumer products. This is due to the flammable electrolyte in lithium-ion batteries. Nanotech Energy, headquartered in the US, has developed a non-flammable graphene lithium-ion battery pack that is both safe and environmentally friendly. They use graphene as the electrode material in the lithium battery and have developed an inexpensive, non-flammable electrolyte called OrganoLyte™. The battery reportedly has an energy density of 162.5 Wh/kg and can withstand over 1400 cycles (nearly 10 years) at 80% capacity. The battery is completely fireproof and suitable for all weather conditions. In contrast, traditional lithium batteries can only withstand 300-500 cycles (approximately two to three years). According to recent news, the company has begun accepting pre-orders, and the battery may be customized for use in electric vehicles, computers, and military applications.
The Future of Graphene Batteries
Tesla recently announced that their Model 3 battery has an energy density approaching 260 Wh/kg. However, it still requires a complex cooling system to prevent overheating, thus taking up considerable space. On the other hand, graphene batteries, because they do not overheat or explode, do not require a cooling system, allowing that space to be used for energy storage batteries in electric vehicles. Following a breakthrough in graphene battery technology, Chinese automaker GAC Motor Co., Ltd. announced the launch of its AION V vehicle, whose graphene battery boasts a range of up to 1000 kilometers and can be charged to 80% capacity in just 8 minutes. Undoubtedly, the continued commercialization of graphene batteries will soon surpass traditional batteries due to their wider applications.
