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Frontiers in
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Winter 2018

Beyond Carbon: The Future of High-Capacity Lithium-Ion Batteries

Researchers stabilize silicon-based battery electrodes to drastically increase battery capacity

Kenneth Madsen

To improve the stability and function of silicon anode batteries, a) amine groups are covalently bound to the silicon nanoparticles. b) These coated particles are then mixed with the conductive component, carbon black, and the polymer binder, polyacrylic acid (PAA). c) Upon mixing in water, the polymer binder and amine groups become charged and engage in ionic bonding, helping maintain contact between the silicon and the current collector. Reprinted with permission from S. Kang et al. (see reference). Copyright 2017 Wiley Publishing.

Following Hurricane Maria and the disastrous tropical storms in the summer of 2017, millions of people in Puerto Rico and the surrounding areas were without electricity in one of the largest blackouts in history. Emergency services and disaster relief efforts suffered from the lack of accessible power due, in part, to an outdated and poorly regulated power grid. Improving the resilience of power grids is essential to combat the dangerous power fluctuations associated with natural disasters. Grid-scale battery installations have been suggested as a buffer to help reduce the severity of these fluctuations. However, to make this idea feasible, batteries with very large energy capacities are needed.

Current lithium-ion batteries, such as the ones in your cell phone, rely on carbon-based materials to store lithium ions when charged. These materials are very reliable, but they suffer from low capacities, making them less desirable for large-scale applications. One promising alternative is to replace the carbon material with silicon, which has a capacity about 10 times greater. Unfortunately, silicon degrades rapidly during charge and discharge, causing the initially high capacity to drop dramatically. To address this problem, scientists at the Center for Electrochemical Energy Science (CEES), an Energy Frontier Research Center, have developed a way to incorporate silicon while mitigating the rapid capacity loss.

Lithium-ion batteries function by storing ions in the anode when charged and releasing them during discharge. During this process, the anode material expands and contracts to accommodate the ions. This repeated volume change often cracks the material. For carbon anodes, the volume change is relatively small, and these detrimental processes are kept under control. Silicon, on the other hand, quadruples in size during charging, leading to extensive cracking. This damage degrades the electrical conductivity within the battery and isolates much of the silicon from the circuit, removing its ability to charge.

To address this problem, CEES scientists developed a molecular layer to cover the surfaces of silicon particles to help maintain good conductivity during these extreme volume changes. This surface modification is composed of two parts: a charged molecule bound directly to the silicon surface, and a polymer binder with the opposite charge surrounding the particles. Because of their opposite charges, the two compounds form ionic bonds with one another. These bonds dynamically respond to volume changes, breaking and re-bonding as the silicon particles change size. This allows the binder to act like glue and connect the silicon particles to the electrically conductive components of the anode.

The CEES researchers observed a striking difference between batteries they constructed with the coated particles, and those without. Without the coating, the batteries retained about 5 percent of their capacity after 400 cycles, whereas batteries with the coating retained 80 percent. As expected, the silicon-based batteries demonstrated much higher capacities than their carbon analogues. The remarkable increase in capacity retention is a testament to the effectiveness of the coating and demonstrates the promise of materials that can dynamically respond to their environment. Batteries are inherently dynamic, and so too must be the methods for bettering their performance. By making use of these strategies, there is the potential to see battery systems with drastically improved capacities that could prove invaluable in improving the reliability of power grids, reducing the severity of dangerous power outages.

More Information

Kang S, K Yang, SR White, and NR Sottos. 2017. “Silicon Composite Electrodes with Dynamic Ionic Bonding.” Advanced Energy Materials 7:1700045. DOI: 10.1002/aenm.201700045


This work was supported as part of the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the Department of Energy, Office of Science, Basic Energy Sciences.

About the author(s):

  • Kenneth Madsen is a Ph.D. student at the University of Illinois at Urbana-Champaign, under the direction of Andrew A. Gewirth, and a member of the Center for Electrochemical Energy Science (CEES), an Energy Frontier Research Center. His research focuses on cathode coatings to stabilize high-voltage lithium-ion batteries.

The Science of Silicon

Adding a binder keeps high-capacity battery’s electrode reliable

Blizzards, hurricanes, and other disasters can leave homes, hospitals, and businesses without power. Batteries could offer relief, but today’s lithium-ion batteries (like the one in a cell phone) don’t store enough energy. Replacing one of the battery’s electrodes with higher-capacity silicon could help, but silicon electrodes are unreliable. They crack. Scientists found a way to keep a silicon electrode together. How? They created a binder. It lets the silicon swell and shrink without losing electrical conductivity. With the new binder, reminiscent of Velcro™, the battery retains about 80 percent of its capacity. Without the binder, it retains 5 percent. The binder lasted for hundreds of charge/discharge cycles. The research offers a novel dynamic bonding scheme to increase battery durability and reliability. Scientists at the Center for Electrochemical Energy Science (CEES), an Energy Frontier Research Center led by Argonne National Laboratory, did the work.

More Information

Kang S, K Yang, SR White, and NR Sottos. 2017. “Silicon Composite Electrodes with Dynamic Ionic Bonding.” Advanced Energy Materials 7:1700045. DOI: 10.1002/aenm.201700045

Disclaimer: The opinions in this newsletter are those of the individual authors and do not represent the views or position of the Department of Energy.