The new cathode technology route further unleashes the potential of all-solid-state lithium batteries

Professor Ma Cheng of the University of Science and Technology of China proposed a new technical route on the cathode material of all-solid-state batteries, which can greatly increase the active material load in the cathode of the complex, so as to more fully realize the potential of all-solid-state lithium batteries in energy density. On March 14, the results were published in Nature Communications.

The use of chloride instead of oxide as the positive active material can greatly increase the active material load in the cathode of the complex Photo courtesy of China University of Science and Technology

Battery technology is at the core of key “dual carbon” technologies such as new energy vehicles and energy storage. All-solid-state lithium battery uses non-flammable inorganic solid electrolyte instead of organic liquid electrolyte, so compared with the current commercial lithium-ion battery, it has higher safety and greater energy density improvement space, and has become the research focus of the next generation of lithium batteries.

In order to give full play to the performance of all-solid-state batteries, its cathode material needs to meet at least two conditions: excellent ion conductivity and good deformability. However, these two points are difficult to achieve in the oxide materials such as lithium cobalt oxide and lithium iron phosphate currently used in commercial lithium-ion batteries: they are brittle materials that are not easy to deform, and the ionic conductivity is generally low.

In this study, Ma Cheng’s research group adopted unconventional material design ideas, selected chloride instead of oxide, and constructed a new cathode material for all-solid-state lithium batteries – lithium titanium chloride.

It has been found that lithium titanium chloride is extremely soft, as long as it is cold-pressed, it can reach a relative density of more than 86.1%, and its room-temperature ionic conductivity is as high as 1.04 millisiemens per centimeter, far exceeding the oxide cathode material, and even compared with the solid electrolyte material mainly responsible for ion transport in the battery.

That is, the cathode of a complex consisting of lithium titanium chloride does not need to contain much solid electrolyte to achieve fairly efficient ion transport and therefore a high active material load. Under the premise of ensuring good cycling performance, the researchers successfully achieved an active material load of 95% mass ratio in the cathode of the lithium titanium chloride composite, which greatly exceeded the limit (usually 70% to 80% mass ratio) of oxide cathodes such as lithium iron phosphate, lithium cobalt oxide, and high-nickel ternary materials. In addition, the lithium titanium chloride compound cathode with such a high active material load demonstrates excellent cycling performance: it achieves stable cycling cycles of up to 2500 cycles at room temperature at a rate of 1 hour of charging or discharging.

These properties show that the almost unexplored chloride cathode material represented by lithium titanium chloride is a very promising cathode “candidate” in all-solid-state lithium batteries, which can further release the potential of all-solid-state batteries in terms of energy density.

The reviewers found lithium titanium chloride “extremely beneficial for the assembly and manufacture of solid-state batteries” and spoke highly of the work, saying: “This discovery is very novel and I think it is a major breakthrough.” (Source: Wang Min, China Science News)

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