What is a solid-state battery and why all the hype?

Written By

Doug Campbell

What is a solid-state battery and why all the hype? 

Solid-state batteries replace two key components of a traditional lithium-ion (Li-ion) battery – a liquid electrolyte and plastic separator – with a single solid ion-conducting material. By employing the right solid material, solid-state batteries promise vast improvements over commercially available state-of-the-art in terms of energy and safety. 

Why the hype?  Simply speaking, “the electrification of everything” is now and the need for high energy, safer and lower cost batteries is at an all-time high and showing no signs of slowing.

To dig deeper, we’ll focus on current Li-ion batteries for reference: 

Lithium-ion

Li-ion batteries have become ubiquitous in our everyday lives powering everything from our cell phones to our numerous wearable/portable devices. Li-ion batteries are the key enabler for “the electrification of everything”. As battery performance improves, the number of applications that can switch to electric power will continue to grow.

Li-ion performance has increased dramatically since its commercial introduction in 1991.  However, this increase in performance has slowed greatly resulting in a case of diminishing marginal returns – i.e. today’s Li-ion batteries can only get so much better. 

To understand why – let’s talk about the components of a typical battery or “cell”. The Li-ion battery today has two active components: the cathode and anode, where lithium sits in its charged and discharged states. However, lithium cannot usefully travel between the cathode and anode without a liquid electrolyte and plastic separator. The electrolyte enables the transport of ions between the electrodes, while the separator assures the movement of ions occurs safely and selectively. Therein lies the challenge with traditional Li-ion batteries; failure of any of these components such as what might occur under abuse conditions (e.g, shorting, crush, overheating, etc.) can result in a very catastrophic failure of the Li-ion cell.  These catastrophic failures are further amplified as the cell energy increases – i.e., as you pack more energy into the same space.  These failure mechanisms have led to numerous well-reported battery fires seen over the past several decades. 

It is important to note that Li-ion cells can be safe provided they:

  1. Are manufactured to sufficient quality standards
  2. Are operated within the well prescribed operational window
  3. Incorporate appropriate control electronics and safety features, typically at the pack-level

However, these engineering and manufacturing features add considerable cost to the overall battery pack.  Thus, the mobile power industry is highly motivated to develop new rechargeable batteries that can break through the energy barrier inherent to current Li-ion while providing considerable safety improvements leading to lower cost battery packs.  Successfully achieving these goals is critical to satisfying our society’s demands for smaller, lighter, and safer devices (cellphones, laptops and EVs).

 

Solid-state

Solid-state, as the name implies, uses a solid material to enable transport of lithium ions in a battery. The benefits of this materials system include:

  • Safety: The solid electrolyte is non-volatile with better heat tolerance, making solid-state batteries inherently safer. While they do indeed fail under abuse conditions, the failure is highly benign without any of the fire or explosion commonly seen in catastrophic failure of Li-ion cells. 
  • Increased energy density: With better energy density comes smaller and lighter devices. With solid-state, you can use higher energy materials – particularly at the anode – allowing vast improvements in the amount of energy storage in a given weight or volume. This will benefit electronics with smaller and lighter devices, but also EVs by increasing electric range. 
  • Simpler packaging and lower cost: Li-ion batteries can be made safer, but only by careful control and packaging. This is particularly true with larger battery packs that are found in electric vehicles. With certain types of solid-state, you are less concerned with high battery temperatures and can potentially remove cooling systems entirely. This in turn opens up certain design constraints and allows cells to be packed more tightly and with less cell package mass and volume. Not only are the resultant batteries higher energy at the individual cell-level, but the improved packaging efficiency means even higher energy at the pack-level. 

Why aren’t solid-state batteries widely available today?

As with any significant new technology advancement, the path from the lab to mass-market is challenging. This is especially true in batteries because electrochemistry, to put it simply, is hard.  As one Advisor once told us, “the tech community is very good at finding new ways to move electrons.  You guys are figuring out new ways to move ions – that’s hard!”

However, at Solid Power we are making great progress. We are taking a leap forward in battery performance and cell size as we build our pilot plant in Colorado. With our new facility on-line, we expect to produce cells at a standard equivalent to those that will power future electric vehicles. Along the way, we will continue our progress towards commercializing solid state batteries in markets like medical, industrial, and aerospace to name a few. We’re excited for the battery-powered future that lies ahead!

Read more about the industry.

Solid State 101