Nanomaterials and Lithium Rechargeable Batteries

Nanomaterials and Lithium Rechargeable Batteries
SEM images of a deposited 250 nm Si film on Cu before (left) and after (right) 30 discharge/charge cycles between 1.2 and 0.02 V at 2.5 C. Credit: (c) Nature Energy (2016). DOI: 10.1038/nenergy.2016.71

Currently, electronic and portable devices use lithium batteries. We get frustrated due to low performance of lithium batteries. Most of the scientists from worldwide have tried to develop lithium batteries with high capacity that are cheap and rechargeable. Although, those batteries even has some drawbacks like the electrode materials shows an artificial change in volume while the process of charging and discharging the battery. This problem sometimes may cause electrode degradation. To overcome this drawback, researchers decided to use nanomaterials for a solution.

Scientists from Stanford University have studied, how nanomaterials create a breakthrough in the field of lithium rechargeable batteries. They found solutions still need to be overcome to make high-capacity rechargeable lithium batteries a practical energy source.

Nanomaterial is said to be as more resistant to mechanical degradation than other materials. It provides solutions for both particle and electrode level.

The nanomaterial can be used as glue for holding the anode particles together at electrode level. The continuous fracturing, cracking, and reforming of the active material leads to electrical disconnection. But, this “glue” can keep the active materials electrically connected by increasing the lifetime of the lithium cell. Amorphous silicon glue has been used to bind Si nanoparticles on an electrode.

Another solution to large volume changes involves producing Nanocomposites or capturing key compounds like sulphur, using yolk-shell nanostructures.

Plagued lithium battery cells have one another problem i.e., the accumulation of a precipitate layer between the solid anode and the electrolyte. Lithium solids develop on the anode surface and creates an electronic insulating layer that conducts lithium ions. This is knowns as the solid-electrolyte interphase or SEI. Because of the volume changes while charging and discharging the SEI becomes unstable and cracks exposing the electrode. This causes more solid growth until the active materials are consumed or degraded. A nanostructured interface, encapsulating the electrode to create a stable interface, or incorporating electrolyte additives are solutions for unstable SEI problems.

Specifically, Lithium anodes are layers to develop dendrites between the anode and the electrolyte. The battery will discharge when dendrites raised to the point that they connect the electrodes. Constructing a protective coating of carbon Nanospheres, constructing an artificial SEI layer, or adding compounds to the electrolyte that inhibits dendrite growth can be a solution of it.

Scientists used Si-C nanofibers, Sn/C composite spheres, and graphene materials to enhance electron and ion movement at the particle level. They also combined different types of Nano-architectures upon a metal current collector. At last, they found current collectors, made by networked materials such as graphene.

Researchers unveiled materials used in any high-capacity electrode that undergoes volume changes will have atom or molecule diffusion loss. This loss is due to solid morphology changes from fracturing or volume expansion and phase changes such as the production of solids. For example, lithium-sulphur batteries often produce polysulfide intermediates that eventually degrade the sulphur electrode.

Nanomaterials provide a potential solution for conventional lithium battery problems that has high capacity. They also have few drawbacks like low density. The additional space between particles shows low density. This is related to the extent that an electrode’s volume will change. And, finally, producing nanoparticle materials is still too expensive to be practical on a commercial scale.

Another problem occurs while binding smaller particles together. This causes increased overall surface area. Large surface area means that more electrolyte solution is consumed at the SEI. This also increases unwanted side reactions.