Modified Cathode Material To Prevent Capacity Loss In Lithium-Ion Batteries

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Lithium-ion(li-ion) batteries are almost everywhere, but they have many problems associated with safety and performance. Researchers across the globe are trying to tackle these issues. One of the major issues with li-ion batteries is that every time a new lithium-ion battery is installed in a device, up to about one-fifth of its energy capacity is lost before the device can be recharged the very first time. 

This is due to the impurities that form on the nickel-rich cathode—the positive (+) side of a battery through which its stored energy is discharged. And this problem is true whether the battery is installed in a laptop, camera, wristwatch, or even in a new electric vehicle.

Researchers from the State University of New York at Binghamton (SUNY Binghamton), Department of Energy’s (DOE’s) Brookhaven (BNL) and Oak Ridge National Laboratories (ORNL) have teamed up to overcome this challenge of capacity loss. They used x-rays and neutrons to test whether treating a leading cathode material (a layered nickel-manganese-cobalt material called NMC 811) with a lithium-free niobium oxide would lead to a longer lasting battery.

“We tested NMC 811 on a layered oxide cathode material after predicting the lithium-free niobium oxide would form a nanosized lithium niobium oxide coating on the surface that would conduct lithium ions and allow them to penetrate into the cathode material,” said Whittingham, now a SUNY distinguished professor and director of the Northeast Center for Chemical Energy Storage (NECCES), a DOE Energy Frontier Research Center led by SUNY Binghamton.

Lithium-ion batteries are made of alternating layers of lithium and nickel-rich oxide materials as nickel is relatively inexpensive and delivers high energy density. But it is unstable and therefore reacts easily with other elements, leaving the cathode surface covered in undesirable impurities that reduce the battery’s storage capacity.

The researchers make niobium-modified nickel after various tests with different metals. The researchers validated it with an experiment. They found that it showed a reduction in first-cycle capacity loss and an improved long-term capacity retention of greater than 93 percent over 250 charge-discharge cycles.

“The improvements seen in electrochemical performance and structural stability make niobium-modified NMC 811 a candidate as a cathode material for use in higher energy density applications, such as electric vehicles,” said Whittingham. “Combining a niobium coating with the substitution of niobium atoms for manganese atoms may be a better way to increase both initial capacity and long-term capacity retention. These modifications can be easily scaled-up using the present multi-step manufacturing processes for NMC materials.”


 

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