5 Volt Electrolyte
ARL-SEDD Docket #10-28; Provisional Patent application filed July 8, 2010
Synopsis of Technology:
The invention describes electrolytes that can support new Li ion chemistries that operates at high voltages (4.7~5 V). Current state-of-the-art electrolyte systems all decompose oxidatively below 4.5 V. By incorporating a series of compounds that bestow desired interphasial properties on high voltage cathode surfaces, the invention enables the development of Li ion batteries that stably deliver energy near 5 V with higher energy density and quality. The potential application of these compounds goes beyond Li ion battery technology and covers any electrochemical device that employs non-aqueous electrolytes for the benefit of high energy density resultant from high operating voltages. The high anodic decomposition limits of the electrolytes developed in the invention are a novel property that no current existing electrolytes possess.
Commercial / Market Potential:
(How can this technology be used in the commercial world)
The primary focus of this invention deals with lithium-ion rechargeable batteries with a wide range of applications. Integration to existing Li ion systems can be easily accomplished, and the development of practical 5 V Li ion cells will be significantly enabled. The benefits of a 5 V power source can be extended to vehicle power, device power, and mobile solider power. Hence, applications can be both military and civilian in nature, and are as numerous as there are devices that can use lithium ion batteries as a power source.
From a commercial perspective, immediate benefits to current lithium battery systems could be realized with the incorporation of the invention into existing electrolyte systems. Extensive results done at ARL have suggested a general improvement in capacity retention and efficiency to all current electrolyte and cathode systems used in Li ion rechargeable batteries.
There are also significant opportunities for the Army in licensing the technology to civilian industry. The initial presentation of part of the data at a DOE review earlier this year has generated intense interest from industry, with companies like DuPont and Honeywell actively in contact with ARL for possible licensing. Many electrolyte manufacturers are currently looking for ways to produce a functional and practical 5 V Li ion electrolyte. It is also expected that these additives will prompt new scientific investigations into the critical interface layer between electrolyte and electrode, advancing our understanding of this and other electrochemical systems. Because this invention relates to general oxidation stability of electrolyte, other electrochemical power devices employing electrolytes will also benefit, including electrochemical double layer capacitors (supercapacitors), electrolytic cells used in electroplating industry, and pseudocapacitors.
Full Technology Description:
The major problem this invention is designed to solve is the anodic decomposition potential of electrolytes. By formulating a series of new solvents and additives, the electrolytes of this invention can delay the onset of decomposition on a cathode surface till > 5 V. The cycling on various cathode surfaces proves that the electrolyte systems can be used to support future 5V battery chemistries. The energy density of Li ion battery is determined by its capacity and cell voltage. The current existing cathode chemistry employed in commercial Li ion batteries operates around 4.0 – 4.2 V. To maximize energy density, researchers have been trying to develop a battery chemistry that operates in the neighborhood of 5 V. So far limited success has been achieved, mostly due to the absence of an electrolyte system that can remain stable in the potential range.
The present invention provides an electrolyte system that remains stable up to 5 V and can effectively support the cell chemistry in prolonged cycles. The invented compounds will provide a highly effective way to reduce the parasitic reactions of electrolytes on a cathode surface at high voltages. These undesired reactions are responsible for loss of capacity during cycling and limit the maximum voltage at which the cell can operate. The invented compounds will enable practical 5 V Li ion battery systems. The benefits of incorporating these compounds in non-aqueous electrolytes include, stabilized interphase without sustaining decomposition of electrolytes, low interphasial impedance with cell cycling and prolonged cycle life. Current known electrolyte systems are unable to fulfill the demands of a 5V Li ion battery.
The results obtained have confirmed that these beneficial effects are universal with various cathode chemistries. During initial laboratory experimentation, the test cell lasted up to 300 cycles when charging to 5 volts. As previously noted, existing commercial cathode chemistries operate in the 4.0 – 4.2 volt range and as such, would not last more than a few cycles at the higher voltage. Moreover, the invention demonstrates high energy capacity during useful cycling. Preliminary t ests show that 83% of initial capacity is retained after 250 cycles. The invention also provides high charge/discharge efficiency. Efficiencies were measured at 99.99% percent after initial cycling. The usefulness of the invention is expected to go beyond Li ion batteries and cover all electrochemical devices that can benefit from high operating voltages.
The key benefits/advantages include:
- Enables the use of higher energy density electrodes and allows power to be delivered at a higher voltage (i.e., 5V vs. 4.0-4.2V).
- Provides significant cycling capabilities at a higher voltage range (5V) while maintaining high energy capacity.
- Up to 300 cycles 5V
- 83% of initial capacity after 250 cycles
- 99.99 efficiency after initial cycling
- Will likely increase number of useful cycles at 4V; estimated 50-100% more cycles at 4V.
- Minimal impact on the current processes in industry; easy to produce and scale up
- Can work with existing battery designs/architectures
- Can reduce need for booster devices in electronic devices
Well developed technology – TRL 6-7. Moreover, cost does not appear to be an issue. No special synthesis technique is required and no rare/expensive materials are used. Only 2~3 steps are required depending on the setup; which makes it easy to integrate and scale with existing processes and architectures. Will facilitate the development the next generation of high voltage (5V) Li ion batteries.
From a February 2007 article on the Lawrence Berkeley National Laboratory website titled, “Batteries of the Future II, Building Better Batteries Through Advanced Diagnostics”,
“For transportation purposes, lithium's very light weight can provide a substantial savings compared to batteries made of heavier metals. Another big advantage of Li ion chemistry is that compared to aqueous batteries such as lead acid, nickel metal hydride, or nickel cadmium, it yields high open-circuit voltage — the higher the voltage, the higher the power and the better the acceleration.” The article further notes, “Lithium ion batteries are already among the most popular for portable electronics, having a superior energy-to-weight ratio and a slow loss of charge when not in use.”
From the website, GreenCarCongress.com, an article titled, “Total Lithium-Ion Battery Sales Forecast To Double By 2012 to US$13.1B” (28 November 2008):
“Market researcher Fuji-Keizai Co. forecasts that global sales of rechargeable batteries for all applications will surge 43% from 2007 to ¥3.61 trillion (US$37.9 billion) in 2012, led by a doubling of lithium-ion battery sales. Sales of lithium ion batteries are seen growing to ¥1.25 trillion [US$13.1 billion] in 2012, about 2.1 times as high as 2007 sales. In addition to use in inexpensive notebook personal computers and power tools, these batteries are expected to be utilized in electric cars and hybrid vehicles.”
The electric vehicle industry represents a substantial and growing market for the next generation Li ion batteries. From another article on the website, GreenCarCongress.com, titled, “Forecast: Lithium-ion Automotive Market Could Reach $1.6B by 2015; Strong HEVs to Dominate” (13 May 2008):
“Dr. Menahem Anderman, the president of Advanced Automotive Batteries, projects that the automotive lithium-ion market could reach $1.6 billion in 2015, up almost five-fold from $337M in 2012, propelled largely by a dramatic expansion in the use of Li ion batteries in strong (or full) hybrid applications.” The following graph illustrates this forecast:
The 2009 International Energy Association (IEA) study, “The Electric and Plug-in Hybrid Vehicle (EV/PHEV) Roadmap” cites a number of forecasts regarding the growth EV/PHEV industry. Additionally, the report lays out projected targets for the growth of the EV/PHEV industry. It details, “ . . .aggressive rates of market penetration once deployment begins. PHEVs and EVs are expected to begin to penetrate the market soon
after 2010, with EVs reaching sales of 2.5 million vehicles per year by 2020 and PHEVs reaching sales of nearly 5 million by 2020. By 2030, sales of EVs are projected to reach 9 million and PHEVs are projected to reach almost 25 million.”
The report also lays out information regarding the factors that will affect consumer behavior and adoption of these types of vehicles. It is highlighted in the following chart:
The non aqueous electrolytes used in existing Li ion batteries operate in the 3.6V – 4.2V range. This invention will allow Li ion batteries to operate in the 5V range; something that is currently impossible with the state of the art electrolytes. Moreover, the invention is expected to improve the number of cycles of the existing, lower voltage electrolytes by 50-100%.