Design principles for enabling an anode-free sodium all-solid-state battery

Abstract

Anode-free batteries possess the optimal cell architecture due to their reduced weight, volume and cost. However, their implementation has been limited by unstable anode morphological changes and anode–liquid electrolyte interface reactions. Here we show that an electrochemically stable solid electrolyte and the application of stack pressure can solve these issues by enabling the deposition of dense sodium metal. Furthermore, an aluminium current collector is found to achieve intimate solid–solid contact with the solid electrolyte, which allows highly reversible sodium plating and stripping at both high areal capacities and current densities, previously unobtainable with conventional aluminium foil. A sodium anode-free all-solid-state battery full cell is demonstrated with stable cycling for several hundred cycles. This cell architecture serves as a future direction for other battery chemistries to enable low-cost, high-energy-density and fast-charging batteries.

Full text

Nature Energy | Volume 9 | September 2024 | 1161–1172 1161
nature energy
https://doi.org/10.1038/s41560-024-01569-9
Article
Design principles for enabling an anode-free
sodium all-solid-state battery
Grayson Deysher1, Jin An Sam Oh 2, Yu-Ting Chen1, Baharak Sayahpour1,
So-Yeon Ham 1, Diyi Cheng1, Phillip Ridley2, Ashley Cronk1,
Sharon Wan-Hsuan Lin 2, Kun Qian 2, Long Hoang Bao Nguyen 2,
Jihyun Jang 2,3 & Ying Shirley Meng 2,4
Anode-free batteries possess the optimal cell architecture due to their
reduced weight, volume and cost. However, their implementation has
been limited by unstable anode morphological changes and anode–liquid
electrolyte interface reactions. Here we show that an electrochemically stable
solid electrolyte and the application of stack pressure can solve these issues by
enabling the deposition of dense sodium metal. Furthermore, an aluminium
current collector is found to achieve intimate solid–solid contact with the
solid electrolyte, which allows highly reversible sodium plating and stripping
at both high areal capacities and current densities, previously unobtainable
with conventional aluminium foil. A sodium anode-free all-solid-state battery
full cell is demonstrated with stable cycling for several hundred cycles. This
cell architecture serves as a future direction for other battery chemistries to
enable low-cost, high-energy-density and fast-charging batteries.
Recent years have shown an increasing demand for electric vehicles
and energy storage devices for large-scale grid applications. Batteries
are critical for enabling these technologies, and although they have
improved substantially since the introduction of the first commer-
cial lithium-ion battery in 19901, further enhancements are needed to
enable higher energy density and lower-cost energy storage systems.
Commonly used lithium is geographically concentrated and has expe-
rienced a rapid increase in price as the demand for batteries grows
2
.
Sodium-based materials, on the other hand, are much less expensive
and more widely available. Whereas sodium batteries are often assumed
to sacrifice energy density in favour of lower cost, in this work we show
that lower-cost sodium batteries may still achieve a high energy density
comparable to current lithium systems due to the natural advantages
of several sodium materials compared with their lithium counterparts.
To compete with the high energy density possessed by lithium-ion
batteries, a considerable change in sodium battery architectures is
needed. A recently popularized idea is the use of an anode-free cell
design3. Unlike conventional batteries, anode-free batteries are
those in which no anode active material is used. Rather than using
carbon- or alloy-based anode materials to store ions during cell charg-
ing, anode-free batteries rely on the electrochemical deposition of
alkali metal directly onto the surface of a current collector (Fig. 1a).
This achieves the lowest possible reduction potential, thus enabling
higher cell voltage, lowers the cell cost and increases energy density
due to the removal of the anode active material (Fig. 1b).
However, many challenges have prevented the use of an anode-free
architecture for both lithium and sodium chemistries. The deposition
of lithium/sodium metal in conventional organic liquid electrolyte
batteries is known to produce a porous or mossy-like morphology4,5.
Additionally, liquid electrolytes commonly react with the deposited
metal forming a solid–electrolyte interphase (SEI)6–9. Continuous
anode morphological changes during cycling inevitably result in the
continuous formation of SEI, which steadily consumes the active mate-
rial inventory
10
. Although several strategies have been explored includ-
ing modifications to the liquid electrolyte
3,11–13
, current collector
14
, cell
stack pressure15 and cycling protocol16, they have yielded only moderate
improvements with many demonstrating only tens of cycles and/or
low initial Coulombic efficiencies (ICE). Instead, a better approach is
Received: 1 November 2023
Accepted: 4 June 2024
Published online: 3 July 2024
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1Program of Materials Science and Engineering, University of California San Diego, La Jolla, CA, USA. 2Department of NanoEngineering, University
of California San Diego, La Jolla, CA, USA. 3Department of Chemistry, Sogang University, Seoul, Republic of Korea. 4Pritzker School of Molecular
Engineering, The University of Chicago, Chicago, IL, USA. e-mail: jihyunjang@sogang.ac.kr; shirleymeng@uchicago.edu
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