What is the holy grail of lithium batteries?

January 15th,

sinopoly Product Page

The research not only describes a new way to make solid state batteries with a lithium metal anode but also offers new understanding into the materials used for these potentially revolutionary batteries.

Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a new lithium metal battery that can be charged and discharged at least 6,000 times ' more than any other pouch battery cell ' and can be recharged in a matter of minutes.

'Lithium metal anode batteries are considered the holy grail of batteries because they have ten times the capacity of commercial graphite anodes and could drastically increase the driving distance of electric vehicles,' said Xin Li, Associate Professor of Materials Science at SEAS and senior author of the paper. 'Our research is an important step toward more practical solid state batteries for industrial and commercial applications.'

One of the biggest challenges in the design of these batteries is the formation of dendrites on the surface of the anode. These structures grow like roots into the electrolyte and pierce the barrier separating the anode and cathode, causing the battery to short or even catch fire.

These dendrites form when lithium ions move from the cathode to the anode during charging, attaching to the surface of the anode in a process called plating. Plating on the anode creates an uneven, non-homogeneous surface, like plaque on teeth, and allows dendrites to take root. When discharged, that plaque-like coating needs to be stripped from the anode and when plating is uneven, the stripping process can be slow and result in potholes that induce even more uneven plating in the next charge.

In , Li and his team offered one way to deal with dendrites by designing a multilayer battery that sandwiched different materials of varying stabilities between the anode and cathode. This multilayer, multi-material design prevented the penetration of lithium dendrites not by stopping them altogether, but rather by controlling and containing them.

In this new research, Li and his team stop dendrites from forming by using micron-sized silicon particles in the anode to constrict the lithiation reaction and facilitate homogeneous plating of a thick layer of lithium metal.

In this design, when lithium ions move from the cathode to the anode during charging, the lithiation reaction is constricted at the shallow surface and the ions attach to the surface of the silicon particle but don't penetrate further. This is markedly different from the chemistry of liquid lithium ion batteries in which the lithium ions penetrate through deep lithiation reaction and ultimately destroy silicon particles in the anode.

But, in a solid state battery, the ions on the surface of the silicon are constricted and undergo the dynamic process of lithiation to form lithium metal plating around the core of silicon.

'In our design, lithium metal gets wrapped around the silicon particle, like a hard chocolate shell around a hazelnut core in a chocolate truffle,' said Li.

These coated particles create a homogenous surface across which the current density is evenly distributed, preventing the growth of dendrites. And, because plating and stripping can happen quickly on an even surface, the battery can recharge in only about 10 minutes.

The researchers built a postage stamp-sized pouch cell version of the battery, which is 10 to 20 times larger than the coin cell made in most university labs. The battery retained 80% of its capacity after 6,000 cycles, outperforming other pouch cell batteries on the market today. The technology has been licensed through Harvard Office of Technology Development to Adden Energy, a Harvard spinoff company cofounded by Li and three Harvard alumni. The company has scaled up the technology to build a smart -sized pouch cell battery.

© Bloomberg Finance LP

Building a Better Lithium Battery

Last year I wrote about A Battery That Could Change The World, which addressed the development of a solid-state lithium battery that won't catch fire if damaged. More recently, I wrote about a different approach to the problem of fires in lithium-ion batteries, which quickly dissipates the heat released from a fire in a cell before it can spread.

Development of better batteries is critical as more electric vehicles hit the roads, and as electric utilities seek better options for storing power from intermittent renewables. In addition, lithium-ion batteries have become ubiquitous in our lives through any number of consumer electronics.

Three key issues that companies are working to address are safety, energy density, and cost. Safety mainly concerns the possibility that lithium-ion batteries can catch fire if damaged. The two aforementioned stories are mostly focused on that aspect of the problem.

The problem of energy density concerns the ability to store energy in a specific volume (or weight). Batteries have low energy density compared to liquid fuels. Gasoline, for example, has about 100 times the volumetric energy density of a Li-ion battery pack. However, the greater efficiency of an electric motor versus a combustion engine substantially narrows the gap for usable energy.

Finally, batteries have historically been an expensive way to store energy. According to the Energy Information Administration, in recent years the cost to install large-scale battery storage systems was typically thousands of dollars per kilowatt (kW). In comparison, the capital costs of producing electricity by power plants can be under $1,000/kW. Importantly, lower battery storage costs would be a critical enabler for utilities seeking to incorporate higher levels of intermittent renewables into the power mix.

It isn't surprising that companies are working to solve each of these battery challenges. But the solution to one problem can create another.

Consider energy density. Lithium-metal batteries allow for much higher energy density than lithium-ion batteries by using lithium-metal electrode instead of graphite electrode. But lithium deposits called dendrites can spontaneously grow from the lithium metal electrodes whenever the battery is being charged. If these dendrites bridge the gap between the anode and cathode (the two opposite electrodes in a battery), a short circuit results. This can cause the battery to fail, which may result in a fire or explosion.

Are you interested in learning more about lithium battery cell? Contact us today to secure an expert consultation!

The lithium-ion battery was a solution to this problem. The dendrite problem can be resolved by replacing the lithium-metal electrode with a carbon electrode that has a layered sheet structure (i.e., graphite), which hosts discrete tiny lithium ions between the layers. However, the result is a lower lithium storage capacity than a battery utilizing a solid, continuous lithium-metal electrode.

Solving the Dendrite Problem

An ideal battery would contain solid lithium electrodes while avoiding the dendrite problem. A company called Zeta Energy, using technology licensed from a top university, believes it has created just such a solution.

I recently spoke to Zeta Energy CEO Charles Maslin, who explained that Zeta is the sixth Greek letter and corresponds to carbon, the sixth element in the periodic table. Zeta potential is also a measure of the effective electric charge on a nanoparticle surface.

In an interview I conducted with Maslin, he provided a description of the new battery along with peer-reviewed data from the 10+ years of research and testing that led to its development.

The key innovation in the Zeta battery is a hybrid anode created from graphene and carbon nanotubes. The resulting three-dimensional carbon anode approaches the theoretical maximum for storage of lithium metal ' about 10 times the lithium storage capacity of graphite used in lithium-ion batteries.

According to published research, the hybrid anode is one of the best-known conductors of electricity, and when the battery is charged, lithium metal is deposited on the sidewalls of the carbon nanotubes and in the pores between the nanotubes. These are chemically bonded to the surface of the graphene that is in turn chemically bonded to a copper substrate. The graphene-carbon nanotube-copper connections introduce no additional electrical resistance that is typically generated at the interface when electrode materials are coated on copper in batteries. This means no heat is generated at this interface.

The combination of a dendrite-free electrode with the seamless interface enables fast charging and discharging of the Zeta battery, unlike in a graphite-based lithium-ion battery where very fast charging can cause lithium dendrites to form on top of graphite. No resistance at the interface means electrons can travel to the electrode much more rapidly. The Zeta battery can thus be charged safely within a few minutes.

More Energy, Less Cost

Despite the breakthrough, building the ideal battery requires more than perfecting the anode. A cathode that matches the high capacity anode is required to unleash the boost in energy density, but current cathodes do not have enough capacity to match the lithium metal anode.

Zeta's second key innovation is a hybrid cathode created from sulfur and carbon, which has 8 times the capacity of current cathodes based on metal oxide. Thus, Zeta's anode-cathode combination means a packaged lithium-sulfur battery with three times the energy storage capacity of lithium-ion batteries.

Further, Zeta has eliminated the use of expensive metals such as cobalt in its battery. That translates to a significant reduction in battery cost. Though others have been trying to develop sulfur-based cathode for decades, they just could not get it to cycle well, and the battery dies after just a couple of hundred cycles at most. Maslin explained that Zeta has succeeded in stabilizing the sulfur cathode and pointed to test results that show it can be cycled with minimal capacity loss over thousands of cycles.

Furthermore, the Zeta lithium-sulfur battery does not self-discharge to any appreciable extent and holds charge for a significantly long time, thus boasting a superb shelf life. A major battery performance concern is self-discharge ' you charge the battery then store it, but when you use it later, only a fraction of the stored battery capacity is left.

Based on Zeta's measurements, it is estimated that more than 90% of its battery capacity will remain after 10 years of storage at full charge, unlike regular lithium-ion batteries that will have at best 10% capacity over the same period of storage. That means the Zeta battery is ready to work after virtually any period of storage.

In summary, the Zeta battery addresses both energy density and safety. Test results published in several scientific journals including Nature Magazine show that the Zeta battery has:

• Up to 3 times the energy storage capacity of lithium-ion batteries

• Faster charge time (minutes instead of hours)

• Lower battery temperature

• Little degradation over charge/recharge cycles

• Outstanding shelf life

• Significantly lighter than lithium-ion batteries

• Zero cobalt

• Significantly lower cost than lithium-ion batteries

Conclusions

If their research and test results are accurate, Zeta Energy may hold the new gold standard in energy storage. The technology appears to address multiple shortcomings of current lithium-ion batteries and has done so at a lower price point. These are exactly the kinds of breakthroughs that are needed if battery storage is to be adopted widely by utilities seeking to smooth out the intermittency of renewables like wind and solar power.

For more aluminium ion battery priceinformation, please contact us. We will provide professional answers.