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Binder-free 3D silicon-nickel electrodes for Li-ion batteries show high capacity and cycling stability

13 November 2012

Master.img-001
Cycling characteristics of 700 nm 3D(Si,Ni) at 1C showing a reversible specific capacity of 1,650 mAh/g after 120 cycles of charge/discharge. Credit: ACS, Gowda et al. Click to enlarge.

Researchers from Rice University and Applied Materials have developed another approach to delivering the theoretically high energy capacity of silicon-based anodes for Li-ion batteries while avoiding the problem of severe capacity fading during cycling associated with the significant volumetric changes resulting from reversible lithium ion insertion.

In a paper published in the ACS journal Nano Letters, they report engineering three-dimensional porous nickel-based current collectors coated conformally with layers of silicon to form high-capacity electrodes. These binder/conductive additive-free silicon electrodes showed excellent electrode adhesion resulting in superior cyclic stability and rate capability. A 700 nm 3D(Si,Ni) material at 1C showing a reversible specific capacity of 1650 mAh/g after 120 cycles of charge/discharge.

The nickel current collector design also allows for an increase in silicon loading per unit area leading to high areal discharge capacities of up to 0.8 mAh/cm2 without significant loss in rate capability.

They attributed the excellent electrode utilization (85%) and improved cyclic stability for the metal/silicon system to reduced internal stresses/fracture upon electrode expansion during cycling and shorter ionic/electronic diffusion pathways that help in improving the rate capability of thicker silicon layers.

Recently the Li ion battery has gained renewed interest as a potential candidate to replace gasoline in vehicular applications...Hence extensive research efforts are underway in search of new battery electrodes to improve the energy density of the Li ion cell.

...there exists a need for the clear understanding and development of stable binder-free Si electrodes that could lead to significant improvements in energy densities and cycling characteristics of silicon based lithium ion batteries. Herein, we demonstrate the ability to fabricate scalable tubular nickel current collectors with variable pore dimension and thickness suitable for thin film battery applications. Conformal amorphous silicon films of different mass loadings have been coated onto the tubular nickel substrates (3D(Si,Ni)) and tested in lithium half cells. The binder free 3D(Si,Ni) electrode has shown improved capacity per unit area and cyclic stability due to the porous structure and excellent electrode adhesion.

—Gowda et al.

To fabricate the material, they deposited porous nickel films on stainless steel substrate by co-electrodepositing Cu−Ni film; selectively etched copper from the microstructure of Cu−Ni films; and conformally coated silicon films within the pores of nickel by chemical vapor deposition process. Two types of porous Ni films (types 1 and 2) with different aspect ratios were fabricated by selective etching of the copper from coelectrodeposited Ni−Cu films; they also deposited silicon of different mass loading on the two types of Ni films.

As one example, a 700 nm type 1 3D(Si,Ni) was tested in lithium half cells for its electrochemical performance. They observed first cycle capacity of 0.36 mAh/cm2—about 85% of the theoretical capacity expected for the corresponding Si loading. An irreversible capacity loss of about ∼28% was observed after the first discharge, due to secondary surface reactions, and a capacity loss of only ∼5% was observed between the second and 120th cycle. A stable reversible capacity of ∼0.22 mAh/cm2 was observed for the 700 nm 3D(Si,Ni).

Type 2 3D (Si,Ni) showed a reversible capacity of ∼0.8 mAh/cm2 at a current rate of 0.05 C with 80% of the reversible capacity retained at four times larger current density of 0.2 C.

The electrochemical method based on pore size and film thickness engineering is scalable and has the potential to control the aspect ratio of the pores which could lead to the development of higher capacity Si anode. The binder free approach of developing scalable, stable Si anodes, could have a huge impact in realizing high energy density lithium ion batteries.

—Gowda et al.

Resources

  • Sanketh R. Gowda, Victor Pushparaj, Subramanya Herle, G. Girishkumar, Joseph G. Gordon, Hemtej Gullapalli, Xiaobo Zhan, Pulickel M. Ajayan, and Arava Leela Mohana Reddy (2012) Three-Dimensionally Engineered Porous Silicon Electrodes for Li Ion Batteries. Nano Letters doi: 10.1021/nl302114j

November 13, 2012 in Batteries | Permalink | Comments (7) | TrackBack (0)

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Comments

Another way to make future improved EV batteries? If lower cost, EV batteries with 1000+ mAh/Kg energy density and 2000+ cycles are mass produced by 2018/2020 or so, it would be the start of the end for most ICEVs, HEVs and PHEVs.

Affordable BEVs with 600 to 1000+ Km range between charges will become game changers.

Also, http://www.greencarcongress.com/2012/11/rice-20121102.html

http://www.greencarcongress.com/2012/07/thankur-20120717.html

.. just market to the public within a FEW months and be believed.

If it's cheap, recharge fast, last long and offer a real long range, then im interrested to buy. I will take a month or two of vacation and i will drive from montreal to winnipeg, calgary, vancouver, mount rushmore, las vegas, san francisco, los-angeles, new orleans, florida, new york and then back to montreal .

You realize once these cells are on the market gasoline will collapse to $1 a gallon again..

Herm,

Gasoline prices are already being held down by the threat of batteries. Too bad everyone is so heavily invested in oil and also only interested in wealth for themselves. Pretty obvious to me the whole country wants someone else to do the work.

This is a three dimensional electrode, so when these guys say 1650 mAh/g, does that include the nickel support structure, and how does one account for the extra space in the electrolyte solution? Depending on how they define the anode, these could be energy dense, but not likely, (the misleading thing is that they report their electrode energy density per mass, not area or volume). I'll bet this has a problem with fast charging due to limitations on ion flow through the porous "current collector".

"Gasoline prices are already being held down by the threat of batteries."(bk4), present and future, is something many people don't discuss - esp. w/ an EV now the Motor Trend Car of the Year.

Binder free? Does that mean there's not a bunch of women? LOL

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