Scientists May Have an Explanation for Battery Longevity Issues
Rechargeable lithium-ion batteries experience degradation over time. They gradually hold less charge, often becoming ineffective. Recent research indicates that unwanted hydrogen protons may play a critical role in this process.
When hydrogen protons occupy molecular spaces in the positive end of the battery, there's less capacity for charged lithium ions. These ions are essential for maintaining battery reactivity and conducting charge. A study published in Science on September 12 highlights this issue.
Chemical Reactions and Energy Loss
The research uncovers undesirable chemical reactions in batteries. Specifically, the electrolyte — which should transport lithium ions — can inadvertently release hydrogen into the cathode, causing energy loss. Gang Wan, a materials physicist at Stanford University, explains the significance: "Even if you’re not using the battery, it loses energy."
Previous theories mainly targeted lithium ion behavior regarding energy depletion. Researchers speculated on hydrogen's influence; however, observing hydrogen has proven difficult due to its small size. To investigate, Wan and his team replaced the electrolyte's hydrogen with deuterium. They used advanced X-ray imaging and mass spectrometry to track the deuterium's movement. These methods confirmed that hydrogen primarily contributes to charge loss in the cathode.
Implications for Battery Design
This research enhances our understanding of battery chemistry, making it important according to Bart Bartlett, a materials chemist at the University of Michigan. Insights suggest chemical adjustments may lead to improved battery lifespan.
Furthermore, this work raises concerns about high-voltage batteries. In striving for smaller, energy-dense batteries, engineers often overlook hydrogen's risks in high-voltage environments. Higher voltage increases reactivity at the cathode, which systematically enables more hydrogen infiltration. "It’s a trade-off we didn't clearly understand," Bartlett noted.
While the study provides valuable insights, it evaluates a specific battery type and situation. Therefore, further investigation is essential to establish a broader understanding of these findings.
If replicable outcomes emerge, researchers like Jacqueline Edge from Imperial College London foresee advancements in battery longevity. These improvements could boost innovations like longer-range electric vehicles. Additionally, enhanced battery life may reduce our reliance on mining for cobalt and lithium, addressing environmental and social issues. Edge refers to this as a two-fold sustainability benefit.
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