In a recently published paper, Stanford professor Yi Cui revealed a new battery design that could, if it proves durable and effective in the real world, be a significant new technology in the energy storage market. Like many experimental battery designs, Cui’s battery uses forms of lithium and sulfur. However, the professor’s battery uses them in a completely novel fashion, sidestepping some of the problems that normally plague lithium sulfur batteries.
To understand why this battery holds so much promise, it’s important to understand the electrochemistry of sulfur. When sulfur is used in a battery, it sometimes produces polysulfides, which can damage the inner workings of the battery. When polysulfides collect within the electrolyte of the battery, they cause the other parts to degrade quickly. That’s why traditional lithium sulfur batteries have such a low cycle life, sometimes lasting only a few dozen cycles.
Cui’s design turns the production of polysulfides on its head: the electrolyte is composed of a lithium polysulfide material. When the battery is discharging, lithium ions leave a lithium cathode and bond with the lithium polysulfide electrolyte. When it’s charging, the ions head back to the lithium metal cathode. The result is a flow battery that, unlike any other flow battery, needs no ion-selective membrane. Instead, a cheap passive coating of the lithium metal allows the correct ions to pass without leading to degradation of the cathode.
The Cui lab at Stanford will be familiar to readers who have read about previous battery work done there. He seems to have an uncanny ability to turn out several new battery chemistry breakthroughs every year, ranging from yolk-shaped encapsulants to silicon nano-rods to dye-based batteries. It seems inevitable that an innovation from the Cui lab will eventually rewrite the energy storage history books.
There’s reason to be hopeful for this particular concept. This battery has two features that resonate with anyone who has tried to understand why flow batteries haven’t succeeded so far: the materials involved (lithium and sulfur) are relatively cheap and the absence of a membrane eliminates another large cost factor for most flow battery designs. If the Cui battery can be scaled up from its small laboratory prototype and can withstand thousands of cycles, this concept could lead to a much cheaper form of energy storage than currently exists.
That’s a big “if.” Many other promising experimental battery designs have proved to be too finicky or too expensive to manufacture to become real-world products. Cui and his graduate student, Guangyuan Zheng, have shown data that their battery can endure 2,000 cycles without any noticeable degradation, which is a good start. But the real proof of the system’s success will be in a commercially manufactured, scaled-up model.
Tags: Advanced Battery Innovations, Grid-Tied Energy Storage, Research & Development, Smart Energy Program
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