APPLICATIONS OF TECHNOLOGY:
Lithium ion rechargeable batteries for
- hybrid electric vehicles
- consumer electronics
- power tools
- Increases energy density by 25% in batteries using silicon negative electrodes
- Potentially doubles energy density when used with high capacity positive electrode materials
- Improves cycling capability
- Improves battery safety
- Prolongs cycle life
- Can be incorporated into existing lithium ion battery manufacturing plants
- Scalable manufacturing using low cost materials
Scientists at Berkeley Lab have invented highly conductive polymer binder materials that significantly improve the viability of using silicon as an electrode material in lithium ion batteries for high power and high energy applications. When used in the fabrication of negative silicon electrodes, the Berkeley Lab binder materials deliver significantly improved battery life. When combined with high capacity positive electrode materials, the conductive binder materials promise to double energy density.
The polymer materials improve the cycling capability of silicon by preventing electrode degradation over time. The polymer binder is highly conductive, thus eliminating the need for conductive additives, and it binds to the silicon particles to maintain good electronic conductivity throughout the electrode. Due to their flexibility, the polymer materials accommodate a battery electrode’s expansion and contraction during charge/discharge. In addition, the Berkeley Lab materials are chemically and mechanically stable (IB-2643).
The scientists have synthesized and further improved a conductive binder material in terms of performance, adhesion strength and swelling. Specifically, the conductive binder provides significantly enhanced adhesion to materials such as graphite, silicon, silicon alloy, tin and tin alloy. A silicon electrode based in this material potentially can deliver silicon's full theoretical capacity, approximately 3,500 mAh/g, with good rate retention (IB-2643A).
In addition, the Berkeley Lab team has identified a low cost fabrication process, using low cost materials, that enables adjustment of their adhesion and electronic properties as well as the degree of swelling (IB-3279).
Until now, silicon-based negative electrodes have not maintained stable capacity during the cycling process. The Berkeley Lab conductive binder technologies better tolerate volume changes during cycling and may be compatible with current manufacturing technology.
Silicon Composite Electrode
The Berkeley Lab team has combined lithium metal with the Berkeley Lab conductive binder plus other materials to create a hybrid electrode system for use in lithium ion batteries. The technology increases the energy density of the lithium ion battery and enables the use of a positive electrode that does not contain lithium ions. The Berkeley Lab technology contributes to improved battery safety by circumventing lithium metal dendrite formation (IB-2890).
Improvements to processing conditions for Berkeley Lab's silicon composite electrode technology have achieved higher energy density and prolonged cycling and storage lifetime by capacity in the electrode (IB-3053).
STATUS: Published Patent Applications WO2010135248 and WO2012047377 available at www.wipo.int. Available for licensing or collaborative research.
DEVELOPMENT STAGE: Proven principle. Sample materials have been tested.
SEE THESE OTHER BERKELEY LAB TECHNOLOGIES IN THIS FIELD:
REFERENCE NUMBERS: IB-2643, IB-2643A, IB-2890, IB-3053, IB-3279