New High-Performance Solid-State Battery Surprises the Engineers Who
Created It TOPICS:Battery TechnologyEnergyNanotechnologyUCSD By UNIVERSITY
OF CALIFORNIA - SAN DIEGO SEPTEMBER 24, 2021
https://scitechdaily.com/new-high-performance-solid-state-battery-surprises-the-engineers-who-created-it/
New
Battery Technology Concept Engineers create a high performance
all-solid-state battery with a pure-silicon anode. Engineers created a new
type of battery that weaves two promising battery sub-fields into a single
battery. The battery uses both a solid state electrolyte and an all-silicon
anode, making it a silicon all-solid-state battery. The initial rounds of
tests show that the new battery is safe, long lasting, and energy dense. It
holds promise for a wide range of applications from grid storage to
electric vehicles. The battery technology is described in the September 24,
2021 issue of the journal Science. University of California San Diego
nanoengineers led the research, in collaboration with researchers at LG
Energy Solution. Silicon anodes are famous for their energy density, which
is 10 times greater than the graphite anodes most often used in today’s
commercial lithium ion batteries. On the other hand, silicon anodes are
infamous for how they expand and contract as the battery charges and
discharges, and for how they degrade with liquid electrolytes. These
challenges have kept all-silicon anodes out of commercial lithium ion
batteries despite the tantalizing energy density. The new work published in
Science provides a promising path forward for all-silicon-anodes, thanks to
the right electrolyte. All-Solid-State Battery With a Pure-Silicon Anode 1)
The all solid-state battery consists of a cathode composite layer, a
sulfide solid electrolyte layer, and a carbon free micro-silicon anode. 2)
Before charging, discrete micro-scale Silicon particles make up the energy
dense anode. During battery charging, positive Lithium ions move from the
cathode to the anode, and a stable 2D interface is formed. 3) As more
Lithium ions move into the anode, it reacts with micro-Silicon to form
interconnected Lithium-Silicon alloy (Li-Si) particles. The reaction
continues to propagate throughout the electrode. 4) The reaction causes
expansion and densification of the micro-Silicon particles, forming a dense
Li-Si alloy electrode. The mechanical properties of the Li-Si alloy and the
solid electrolyte have a crucial role in maintaining the integrity and
contact along the 2D interfacial plane. Credit: University of California
San Diego “With this battery configuration, we are opening a new territory
for solid-state batteries using alloy anodes such as silicon,” said Darren
H. S. Tan, the lead author on the paper. He recently completed his chemical
engineering PhD at the UC San Diego Jacobs School of Engineering and
co-founded a startup UNIGRID Battery that has licensed this technology.
Next-generation, solid-state batteries with high energy densities have
always relied on metallic lithium as an anode. But that places restrictions
on battery charge rates and the need for elevated temperature (usually 60
degrees Celsius or higher) during charging. The silicon anode overcomes
these limitations, allowing much faster charge rates at room to low
temperatures, while maintaining high energy densities. The team
demonstrated a laboratory scale full cell that delivers 500 charge and
discharge cycles with 80% capacity retention at room temperature, which
represents exciting progress for both the silicon anode and solid state
battery communities. Silicon as an anode to replace graphite Silicon
anodes, of course, are not new. For decades, scientists and battery
manufacturers have looked to silicon as an energy-dense material to mix
into, or completely replace, conventional graphite anodes in lithium-ion
batteries. Theoretically, silicon offers approximately 10 times the storage
capacity of graphite. In practice however, lithium-ion batteries with
silicon added to the anode to increase energy density typically suffer from
real-world performance issues: in particular, the number of times the
battery can be charged and discharged while maintaining performance is not
high enough. Much of the problem is caused by the interaction between
silicon anodes and the liquid electrolytes they have been paired with. The
situation is complicated by large volume expansion of silicon particles
during charge and discharge. This results in severe capacity losses over
time. “As battery researchers, it’s vital to address the root problems in
the system. For silicon anodes, we know that one of the big issues is the
liquid electrolyte interface instability,” said UC San Diego
nanoengineering professor Shirley Meng, the corresponding author on the
Science paper, and director of the Institute for Materials Discovery and
Design at UC San Diego. “We needed a totally different approach,” said
Meng. Indeed, the UC San Diego led team took a different approach: they
