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Is Solid-state Really a Threat to Lithium-ion Batteries?

The electric vehicle (EV) industry is continuing to grow at a rapid rate, resulting in battery innovation occurring at an all-time high. Batteries are the driving force behind EVs, so it makes sense that large sums of money are being invested into researching and developing a battery that provides better functionality and capabilities than those currently available within the market.

The Battery

A battery is a conglomerate of multiple cells and consists of three major components:

  1. The positive electrode (cathode)
  2. The negative electrode (anode)
  3. The electrolyte

These components work together within the battery to create a chemical reaction once the battery is connected to an external circuit. This chemical reaction in turn works to produce electrical energy which can be used to power a device connected to the external circuit, such as an electric vehicle.

Side Note:
A battery is a device that converts chemical energy to electrical energy via the flow of electrons from one electrode to another. This process starts with a reaction that takes place between the anode and the electrolyte (a liquid, wet gel or solid that is capable of transporting ions between the reactions that take place at each electrode), resulting in a build-up of electrons at the anode. These electrons want to flow out of the anode and move into the cathode but cannot pass through the electrolyte. This means that the electrons must travel around an external circuit to reach the cathode. This flow of electrons around the external circuit produces an electric current which powers a connected device, such as a motor. It is also important to note that positively charged ions flow through the electrolyte which balances the flow of electrons between the anode and cathode.

Lithium-ion batteries are currently the most popular battery type to use within EVs, with the technology nearing the peak of its performance capabilities. However, there is a new player in the battery space which threatens to trump the function of lithium-ion batteries; the solid-state battery.
Solid-state vs Lithium-ion batteries

A solid-state battery uses solid electrodes and a solid electrolyte, with these components usually made from glass or ceramics. This is different to the majority of other EV batteries including lithium-ion which use liquid and or wet gel components. Due to this use of solid components, the battery type has been shown to elicit several advantageous characteristics:
 

  • Potentially capable of higher power and energy densities than current alternative solutions.
  • Displays a greater tolerance to higher temperatures
  • Allows for faster recharging
  • Smaller and lighter than other forms of electric vehicle batteries.

The biggest advantage that is associated with solid state batteries, however, is their enhanced safety. Solid-state batteries are non-flammable due to its solid components, removing the possibility for the battery to leak or catch fire. This subsequently results in the battery not requiring cooling elements, separators and casing that would normally protect the battery from catching fire. This removal of protective casing and material results in the battery size being dramatically reduced, which in turn can provide one of two possible advantages:
 

  1. Reduces the battery size whilst retaining the same range resulting in reduced production costs.
  2. Maintaining the larger battery size whilst which elicits an increased vehicle range

This safety advantage associated with solid-state batteries directly opposes the major disadvantage that is associated with lithium-ion batteries, which is their safety.

With lithium-ion batteries using liquid components, as well as having low thermal stability, there is a possibility that the battery will leak or catch fire.

But are lithium ion batteries really in danger of being overtaken by solid state batteries? Afterall, they are the most commonly used battery type in EVs, and the performance they provide is impressive.

The main advantage of the lithium-ion battery is the high energy density they possess, which make them very suitable for use in EVs. Additional advantages include:
 

  • Superior self-discharge rate
  • Require no maintenance to ensure they perform
  • Do not require priming
  • There is a variety of Lithium-ion battery types that showcase different characteristics

So, with both battery types offering up appealing advantages to EV manufacturers, why are solid-state batteries not being used?


The problem with Solid-State batteries

Speculating about the advantages that solid-state batteries can provide to EVs is all well and good, but have they actually been demonstrated? The answer at this time is no, with a solid-state battery that is capable of automotive operation not yet developed. This means research and development is still very much on-going.  
The main problem is that no one has been able to produce a solid-state battery that is efficient enough, of the appropriate size, and within a reasonable cost to be used in an EV. Because of this, the core characteristics of a solid-sate EV battery cannot be described.

Separate from this fact, other problems associated with solid-sate include:

 

  • Operation at lower temperatures has been challenging (essential for EV use)
  • An inability to find a solid material that is conductive enough to be used in a large battery
  • They have been found to show very poor performance which render their use in rechargeable batteries very impractical
  • They exhibit low current output which is considered one of the biggest hurdles to overcome for EV operation

With solid-state batteries showcasing some characteristics that could be advantageous to EVs, the research and development are not yet there to make them a viable option for use. Lithium-ion battery technology, on the other hand, is at its peak and their use in EVs results in impressive and continually improving functionality.

Although there could be improvements to Lithium-ion batteries, such as increased safety and manufacturing costs, major brands such as VW, Mercedes and Tesla continue to use them and plan to do so for many years to come. So, while solid-state may be the leading alternative for EVs, we’ll just have wait and see to find out if it’s a possible solution.