Image credit: B. Wang via Physics World

Chinese Researchers Announce 711 Wh/kg Lithium Battery

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Lithium-ion batteries today struggle to reach an energy density of 300 Wh per kilogram. That’s too low for the long range electric vehicles many drivers crave, or for applications that require high power with low weight, such as aircraft. In a recent issue of Chinese Physics Letters, researchers Quan Li, Yang Yang, Xiqian Yu, and Hong Li of the Institute of Physics at the Chinese Academy of Sciences in Beijing, write that they have manufactured practical pouch type rechargeable lithium batteries by using an ultra-thick high discharge capacity cathode with an areal capacity exceeding 10 mAh/cm2 and a lithium metal anode.

The high charge/discharge voltage of the lithium-rich manganese-based oxides allows for a higher lithium-ion storage capacity, the researchers say. The scientists identify Li1.2Ni0.13Co0.13Mn0.54O2 as the chemical composition of the high capacity cathode.

“The anode electrode employs ultrathin metal lithium incorporated using a separator coating technique, which addresses the annoying issue of reversible deposition of ultrathin lithium of large surface capacity,” explains first author Quan Li.

The devices boast a gravimetric energy density of 711.3 Wh/kg and a volumetric energy density of 1653.65 Wh/L, both of which are the highest in rechargeable lithium batteries based on an intercalation-type cathode, Li tells Physics World.

“With respect to the battery manufacture, our extremity battery structure design (including the use of ultrathin current collectors) was tailored to minimize the usage of auxiliary materials while enhancing the proportion of active materials in the entire battery,” he adds. “This synergistic approach is what enabled the ultrahigh energy density of the batteries.” In the abstract for their research paper, the scientists write:

“High energy density rechargeable lithium batteries are being pursued by researchers because of their revolutionary potential nature. Current advanced practical lithium ion batteries have an energy density of around 300 Wh per kg.

“Continuing to increase the energy density of batteries to a higher level could lead to a major explosion of development in some fields, such as electric aviation. Here, we have manufactured practical pouch-type rechargeable lithium batteries with both a gravimetric energy density of 711.3 Wh/kg and a volumetric energy density of 1653.65 Wh/L.

“This is achieved through the use of high performance battery materials including a high capacity lithium rich manganese based cathode and a thin lithium metal anode with high specific energy, combined with extremely advanced process technologies such as high-loading electrode preparation and lean electrolyte injection.

“In this battery material system, the structural stability of cathode material in a widened charge/discharge voltage range and the deposition/dissolution behavior of interfacial modified thin lithium electrode are studied.”

The new devices could benefit long range electric vehicles and electric aviation, both of which place increasingly high demands on battery energy density. The research could also help address some of the inherent issues associated with battery technology, says Li.

“For instance, it offers insights into how to balance safety and other important factors in high energy density batteries, which will help in the practical realization of high energy density batteries in the future. Research on batteries with energy densities approaching theoretical limits will also help improve our knowledge of solid-state ionics and solid-state electrochemistry, allowing perhaps for technological innovation in new materials and battery systems.”

The researchers explain that a trade-off always exists between the energy density, cycle performance, rate capability, and the safety of lithium-ion batteries. Safety is a primary requirement, but elevated energy density will increase the risks during battery operation, they say. “Energy density must be gradually improved while ensuring safety,” says Li. “Our goal is to enhance battery safety performance through solid state battery technology, making high energy density batteries more practical.”

The cycle performance of high energy density batteries also still lags behind that of currently commercialized batteries, he adds. “This parameter needs to be comprehensively considered to meet the requirements of specific fields. It will therefore take considerable time for ultra high energy density batteries to be practically applied. Addressing the challenges that hinder their practical usage will be the direction the researchers will pursue in the future.”

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Lithium Leads

711 Wh/kg is a remarkable feat. Yes, it has only been achieved in the laboratory, but take a look at that chart at the top of this story. Notice anything interesting? The trend toward more energy-dense batteries is speeding up, and one of the leaders is Jeffrey Dahn and his team of battery researchers at Dalhousie University in Halifax, Nova Scotia. CleanTechnica readers will recall that Dahn is one of the battery researchers retained by Tesla to keep it abreast of the latest technology advances.

The time between discoveries in the lab and commercial production is getting shorter as well. Over vegan kebabs in the CleanTechnica grill room, the scuttlebutt is that by 2030, batteries with 1000 Wh/kg energy density will be commonplace and 1500 Wh/kg will be right around the corner. By then, most commercial aircraft will be battery powered, as will the majority of coastal shipping.

Just a few days ago, CATL announced what it calls a “condensed” battery with 500 Wh per kilogram energy density which it thinks may be the tipping point at which battery-powered airplanes become commercially viable, at least for regional flights.

CnEVPost reports the new battery contains a micron scale adaptive mesh structure that regulates inter-chain interaction forces for changes in the electro-chemical reactions of ultra-high energy density chemistries, according to Wu Kai, chief scientist for CATL. The battery also introduces a series of innovations in isolation films as well as innovative processes, including a high energy cathode and a new type of anode, he said.

But we shouldn’t lose sight of the fact that batteries with higher energy density may be more costly than batteries with less sophisticated technology, at least until economies of scale kick in. Recently Nio said it will introduce a 150 kWh battery pack with an energy density of 360 Wh per kilogram for its upcoming ET7 that will cost the same as an entire ET5 automobile which sells in China for RMB 328,000 ($47,580).

No doubt manufacturers will use different batteries for different use cases. Cost may dictate using lower density batteries for entry level cars and trucks and more expensive batteries with higher energy density for premium models. It’s not hard to imagine Volkswagen will use completely different batteries for its upcoming ID.2all than what Porsche chooses for its Taycan.

The good news for those who are watching the EV revolution transpire is that better batteries with longer range are coming. When we look back to today in 2030, we will be amazed at how far the world of electric cars has come in just a few short years. We can’t wait!

A tip of the hat to Dan Allard who took time out from running his farm to share this story with us. 

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Steve Hanley

Steve writes about the interface between technology and sustainability from his home in Florida or anywhere else The Force may lead him. He is proud to be "woke" and doesn't really give a damn why the glass broke. He believes passionately in what Socrates said 3000 years ago: "The secret to change is to focus all of your energy not on fighting the old but on building the new." You can follow him on Substack and LinkedIn but not on Fakebook or any social media platforms controlled by narcissistic yahoos.

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