Nickel foil gold plating is a key material for new solid-state lithium batteries

In the current era where electric vehicles are becoming increasingly "hot", the materials for batteries are also becoming more diverse.

There are different options for battery materials in electric vehicles, such as solid-state lithium batteries.

A special material - nickel foil - can fully charge a standard electric vehicle battery in about 10 minutes by adding a thin layer of nickel inside the battery. This can provide a more economical alternative for electric vehicles equipped with multiple expensive battery packs.

For example, in traditional long-distance electric vehicle travel, a battery pack with a capacity of 120 kWh and requiring one hour to fully charge can be replaced with a battery pack with a capacity of 60 kWh and only charging for 10 minutes, and the range of the two remains very close.
With the rise of the electric vertical takeoff and landing (eVTOL) concept, the industry's unique requirements for battery performance have also brought great challenges. Compared with EV power batteries that run on the road, in addition to energy density and output power, we also need to consider the performance of eVTOL batteries in fast charging efficiency, cycle life, and most importantly, battery safety.
In recent years, we have seen an increasing number of eVTOL projects. Its main focus is on short distance urban air traffic services to avoid congestion on ground roads.

In addition to optimizing the body design of the vehicle, eVTOL batteries with excellent performance in all dimensions are also an indispensable part of such projects.

For example, the energy density of a battery needs to be high, but its volume is also important and it needs to be quite lightweight. And during takeoff and landing, such batteries must be able to output sufficiently high power.

The good news is that in an article published in the journal Joule, Chao Yang Wang, an automotive, mechanical, and chemical materials engineer and director of the Electrochemical Power Center at Pennsylvania State University, stated:

The lithium ion with nickel foil studied not only enables fast charging, but also maintains a range of 80 kilometers.

To achieve a reasonable cost target, eVTOL must be able to withstand 15 trips during peak hours in the morning and evening.

For example, traveling from a city to an airport, carrying 3-4 passengers and flying approximately 80 kilometers.

But in order to achieve ideal goals in multiple aspects, there are obviously many constraints. For example, fast charging often results in fewer cycles of battery charging, while high energy density can reduce charging speed.

However, now the research team led by him has developed a prototype battery that can achieve an eVTOL range of 80 kilometers, an energy density of 271 Wh/kg, fast charging in 5-10 minutes, and 2000 charge discharge cycles.
Chao Yang Wang stated that they have developed the first commercially viable version of eVTOL batteries. He and his colleagues spent about 10 years, from accidentally discovering the idea of batteries to developing various battery prototypes for demonstration.

And their biggest challenge is to minimize the complexity of these self heating structures as much as possible. For this purpose, scientists introduced nickel foil with a thickness of 10 microns into the battery to help it quickly heat up to 60 ℃, achieving optimal fast charging efficiency without forming lithium dendrites that could puncture the internal cells.
    
In addition, heating can also help alleviate the problem of eVTOL batteries not allowing complete discharge during operation, as the system needs to reserve a portion of power to meet the high-power demand during takeoff and landing phases.

But when the battery is fully charged, its charging resistance is relatively low. When there is more remaining power, the charging speed will also be slower. Fortunately, when heating the eVTOL prototype battery, we found that this helped it quickly release remaining energy and enable fast charging.

Chao Yang Wang stated that the speed of this self heating technology is 1-5 ℃ per second. Even for every 10 ℃ increase in temperature, its energy consumption is only 0.8%.

At the same time, the nickel foil embedded in eVTOL batteries will only increase the weight and volume by less than 1.5%, and the additional cost by less than 0.3%.

At present, the research team is trying to apply this solution to electrochemical applications with higher energy density, and their goal is to create the next generation eVTOL battery with an energy density of up to 350-400 Wh/kg, supporting fast charging in 5-10 minutes, and a cost as low as $50/kWh.