Oct 9 2020
Although electric vehicles have been garnering widespread popularity, their long charging time is a major disadvantage for potential customers.
The black phosphorous composite material connected by carbon-phosphorus covalent bonds has a more stable structure and a higher lithium-ion storage capacity. Image Credit: Shi Qianhui, Dong Yihan, and Liang Yan.
With a 5-minute refuel, a standard SUV with a combustion engine can travel 300 miles; by contrast, an advanced electric vehicle takes around 1 hour to store energy sufficient to travel the same distance.
It has been challenging to develop the technology for a high-capacity lithium-ion battery that charges fast and works efficiently, but scientists are currently closer than ever.
An international research team reported details of a specially designed electrode material that enables such advanced batteries in the Science journal on October 8th, 2020.
The combination of high energy, high rate, and long cycle life is the holy grail of battery research, which is determined by one of the key components of the battery: the electrode materials. We aim to search for an electrode material that can make a dent in performance metrics from laboratory research and can hold the promise to stand with the industrial production techniques and requirements.
Hengxing Ji, Professor, University of Science and Technology of China
In the battery, energy enters and exits through electrochemical reactions in electrodes, so effective and efficient Lithium-ion transfer is crucial, says first author Hongchang Jin of University of Science and Technology of China (USTC), particularly in shifting the energy from the battery to the device through the anode.
The scientists resorted to using black phosphorus, a material that has previously been examined for use in electrodes but is often neglected as it tends to deform along its layered edges, which makes the shifting of lithium-ions highly ineffective and leading to material of lower quality.
By integrating graphite with black phosphorus, the chemical bonds between the two materials stabilize and avoid the disturbing edge variations.
Also, the researchers addressed one more problem that hampers the material: Electrolytes can disintegrate into less conductive pieces and accumulate on the electrode’s surface, thereby preventing lithium-ion transfer into the electrode material, such as dust obscuring light through glass.
The researchers employed a thin polymer gel coating to the electrode materials and strengthened the lithium-ion transport path, thus avoiding the problem effectively.
The composite anode material restored 80% of its full capacity in less than 10 minutes and shows a 2000-cycle operation life at room temperature, which was measured at conditions compatible with the industrial fabrication processes.
Sen Xin, Study Co-First Author and Professor, Institute of Chemistry, Chinese Academy of Sciences
Xin continued, “If scalable production can be achieved, this material may provide an alternative, updated graphite anode, and move us toward a Lithium-ion battery with energy density of more than 350 watts-hour per kilogram and fast-charging capability. Successful projection of the above parameters onto the electric vehicle will significantly raise its competitiveness against the fuel cars.”
The 350 W⋅h/kg is the battery’s energy capacity—an electric vehicle fitted with such a battery can travel 600 miles with a single charge. In comparison, the on-market Tesla Model S can travel 400 miles on a single charge.
According to Ji, using the innovative technology, the team intends to seek both basic scientific questions of the lithium-ion charging-discharging process as well as industry-related questions on methods to extend composite material production in more gentle conditions.
We will investigate engineering materials of rationally selected structure, but with consideration for price and practicality to achieve an attractive performance.
Hengxing Ji, Professor, University of Science and Technology of China