Tech Insights

High-Nickel Battery Cathodes Show Superior Cycle Life Performance

June 20, 2023 by Shannon Cuthrell

Researchers from Idaho National Laboratory found that a high-nickel content battery cathode, NMC811, demonstrates superior cycle life performance over lower-nickel content materials. 

Researchers at Idaho National Laboratory (INL) recently found that nickel-rich cathode materials demonstrate superior cycle performance in electric vehicle charging. 

 

Researchers test new EV charging technology at Idaho National Laboratory

Researchers test new EV charging technology at Idaho National Laboratory. Image used courtesy of INL

 

The researchers focused on NMC811, a common composition of 80% nickel, 10% manganese, and 10% cobalt, comparing its degradation and performance characteristics to NMC532, composed of half nickel, 30% manganese, and 20% cobalt. Overall, they concluded NMC811’s transport properties and cycle performance surpass NMC532 materials with lower nickel content. 

The findings come as the EV industry is testing and deploying new battery chemistries offering higher performance and charging capabilities, as limited range and slow charging times remain critical barriers to widespread EV adoption. 

 

NMC811 vs. NMC532: Which Performs Better? 

NMC cathode chemistry is nothing new, tracing back to research in the 1980s. INL researchers wanted to compare NMC811’s performance to NMC532—a common battery material when the team started the project over five years ago, as noted by INL

They tested NMC811 aging under fast-charging conditions that translate to over 200,000 miles of driving in the most extreme tests. Analyzing battery cells charged between 35% and 100%, they studied how the particles can crack under different cycling conditions. 

The study—published in Advanced Energy Materials—zooms in on the critical aging mechanisms for NMC811 at extreme charging levels from 1 C-rate to 9 C for up to 1,000 cycles. (For context, C-rates refer to a battery’s charge/discharge rates, with 1 C equating to a 0-100% charge in an hour.)

The researchers employed various electrochemical and microscopy techniques to determine the NMC cathode’s chemical, structural, and crystallographic degradation as it was subjected to different cycling conditions. They found NMC811 has 4.6 to 3.15 times as much capacity reduction than NMC532 in charging between 4 C and 6 C, translating to 15 minutes and 10 minutes, respectively. 

 

Idaho National Laboratory’s battery research facility.

Idaho National Laboratory’s battery research facility. Image used courtesy of INL

 

Compared to NMC532, NMC811 showed a greater subsurface crystallographic degradation with a similar level of subparticle cracking. Still, it outperformed its lower-nickel-content counterpart, despite those degradations, due to its superior transport properties and particles with radially oriented grains. These benefits to the particle arrangement and conductivity mean the battery can hold higher charge levels. NMC811 also has a higher specific energy, referring to the level of energy the battery can hold relative to its mass. 

INL’s press release also noted that NMC811 has slower impedance growth, meaning it delivers a high current on demand since it has low internal resistance causing the battery to heat up, which would negatively affect cell capacity and voltage. 

 

Market Context: Demand for Faster Charging Capabilities 

According to the International Energy Agency (IEA), EV sales grew by 55% in the U.S. last year, accounting for nearly 8% of all car sales. Battery-electric vehicles (BEVs) led the American market, rising by 70% to nearly 800,000, while plug-in hybrid EVs increased by 15%. Electric car stock jumped to 3 million, up 40% from 2021. 

Despite EVs’ growing uptake in the U.S., competing with traditional gas-powered cars means building longer-lasting components and higher charging cycle capacity. Drivers want a refueling experience comparable to that of a conventional vehicle. But even the fastest option on the market, direct-current (DC) fast-charging, takes 20 minutes to an hour to charge a BEV from empty, according to the U.S. Department of Transportation. Level 1 and Level 2 connectors typically take 40-50 hours and 4-10 hours, respectively, to charge a BEV to 100%. DC fast-charging is estimated to yield 180 to 240 miles of range per hour of charging. 

 

types of materials in different anodes and cathodes

A breakdown of the types of materials in different anodes and cathodes. Image used courtesy of the International Energy Agency
 

NMC batteries are one of a growing number of alternatives to conventional battery chemistries. In fact: NMCs had a dominant share of the battery market in 2022, topping 60%, according to the IEA. Lithium-iron-phosphate (LFP) batteries followed with a share of nearly 30%, while nickel-cobalt-aluminum oxide (NCA) accounted for 8%. 

LFP batteries represent a compelling competitor to NMCs. According to Battery University, they have a cycle life of 2,000 or higher compared to 1,000 to 2,000 for NMCs, depending on the temperature and depth of discharge. Automakers like Tesla are switching to LFPs, now featured in most standard-range Tesla Model 3 and Y EVs.