Lithium–silicon battery

Lithium–silicon batteries are a lithium-ion battery technology under development that employ a silicon anode.[1] Silicon has a much larger energy density than currently used anode materials, but the large volume change of silicon when lithium is inserted is the main obstacle to commercializing this type of anode material.

History

The first laboratory experiments with lithium-silicon batteries took place in the late 1990s.[2] The large volume change of silicon when lithium is inserted is the main obstacle to commercialization this type of anode material.[3]

Silicon-graphite composite electrodes

Test sample production of batches of batteries using a silicon-graphite composite electrode started by the company Amprius in 2014.[4] The same company claims to have sold several hundred thousands of these batteries as of 2014.[5] In 2016, Stanford University researchers presented a method of encapsulating silicon microparticles in a graphene shell, which confines fractured particles and also acts as a stable solid electrolyte interface layer. These microparticles reached an energy density of 3,300 mAh/g.[6]

Also in 2014, a company called Enevate presented a battery using an unknown monolithic silicon-composite anode with a low cell resistance.[7] These batteries leave 25% of the capacity unused, most likely to reduce fast degrading of the cell.[8] For this technology it was named an Innovation Award Honoree in three categories at 2016's Consumer Electronics Show (CES).[9] Shortly after CES 2016, it was announced that Sonim Technologies (a company selling rugged mobile phones) will be using Enevate's lithium-silicon batteries in its products.[10]

Specific capacity

Specific capacity and volume change for some anode materials (given in their lithiated state).[3][11][12]
Anode material Specific capacity (mAh/g) Volume change
Li 3862 -
LiC
6		 372 10%
Li
13Sn
5		 990 252%
Li
9Al
4		 2235 604%
Li
22Si
5		 4200 320%

A crystalline silicon anode has a theoretical specific capacity of 4200 mAh/g, more than ten times that of anodes such as graphite (372 mAh/g).[3] Each silicon atom can bind up to 4.4 lithium atoms in its fully lithiated state Li
4.4Si, compared to the one lithium atom per 6 carbon atoms for the fully lithiated state of graphite, LiC
6.[13]

Silicon swelling

The lattice distance between silicon atoms multiplies as it accommodates lithium ions (lithiation), reaching 320% of the original volume.[3] The expansion causes large anisotropic stresses to occur within the electrode material, leading to fractures and crumbling of the silicon material and ill-fated detachment from the current collector.[14] Prototypical lithium-silicon batteries lose most of their capacity in as little as 10 charge-discharge cycles.[2][15]A solution to the capacity and stability issues posed by the significant volume expansion upon lithiation is critical to the success of silicon anodes.

Recent research has pointed to silicon nanostructures as a potential solution. A group at Stanford university created silicon nanowires on a conductive substrate for an anode, and found that not only does the nanowire morphology create direct current pathways to help increase the charge flow of the battery, but it also allows for the decreased disruption from volume change.[16] However, the large volume change of the nanowires can still pose a fading problem for the anode, and active research on increasing anode lifetime and reliability.

Other studies have examined the potential of silicon nanoparticles. Anodes that use the comparatively inexpensive silicon nanoparticles may overcome the price and scale barriers of nanowire batteries, while also having more mechanical stability over cycling compared to typical silicon electrodes.[17] Typically, these anodes also use carbon as a conductive additive and a binder for increased mechanical stability. However, this geometry does not fully solve the issue of large volume expansion upon lithiation, exposing the battery to increased risk of capacity loss from inaccessible nanoparticles after cycle-induced cracking and stress.

Another nanoparticle approach is using conducting polymers as both the binder and the additive for nanoparticle batteries. One study examined a three-dimensional conducting polymer and hydrogel network inside which silicon nanoparticles reside.[18] The framework resulted in a marked improvement in electrode stability, with over 90% capacity retention after 5,000 cycles. However, the potential for inexpensive scale up has not been thoroughly investigated. Researchers at Trinity College in Dublin, Ireland offered another potential solution, utilizing slurry coating techniques – which are currently employed at large scales for electrode production – with a conducting polymer binder.[19] In general, the conducting polymer additive provides both mechanical stabilization and an avenue for conduction, replacing the conventional two-material system of a polymer stabilizer and carbon black particles. The substitution allows both better stabilization and better conduction.

Solid electrolyte interface layer

SEI layer formation on silicon. In green on the left, the normal battery operation, in blue the SEI layer formation. The electrolyte decomposes by reduction.

Another factor that prevents commercialization of lithium-silicon batteries is the development of an unstable solid electrolyte interface SEI layer consisting of decomposed electrolyte material.[20]

The SEI layer would normally form a layer impenetratable for electrolyte, which prevents further growth. However, due to the swelling of the silicon, the SEI layer cracks and become porous.[21] Thus, it can grow to into thicker layers. A thick SEI layer results in a higher cell resistance, which decreases the cell efficiency.[22][23]

The SEI layer on silicon is composed of reduced electrolyte and lithium.[22] At the operating voltage of the battery, the electrolyte is unstable and decomposes.[20] The consumption of lithium in the formation of the SEI layer further decreases the battery capacity.[23] Limited growth of the SEI layer is therefore an important property needed to design commercial lithium-silicon batteries.

See also

References

  1. ↑ Nazri, Gholam-Abbas; Pistoia, Gianfranco, eds. (2004). Lithium Batteries - Science and Technology. Kluwer Academic Publishers. p. 259. ISBN 1-4020-7628-2.
  2. 1 2 Bourderau, S; Brousse, T; Schleich, D.M (1999). "Amorphous silicon as a possible anode material for Li-ion batteries". Journal of Power Sources. 81-82: 233. doi:10.1016/S0378-7753(99)00194-9.
  3. 1 2 3 4 Mukhopadhyay, Amartya; Sheldon, Brian W. (2014). "Deformation and stress in electrode materials for Li-ion batteries". Progress in Materials Science. 63: 58. doi:10.1016/j.pmatsci.2014.02.001.
  4. ↑ St. John, Jeff (2014-01-06). "Amprius Gets $30M Boost for Silicon-Based Lithium-Ion Batteries". Greentechmedia. Retrieved 2015-07-21.
  5. ↑ Bullis, Kevin (10 January 2014). "Startup Gets $30 Million to Bring High-Energy Silicon Batteries to Market". MIT Technology Review.
  6. ↑ Li, Yuzhang; Yan, Kai; Lee, Hyun-Wook; Lu, Zhenda; Liu, Nian; Cui, Yi (2016). "Growth of conformal graphene cages on micrometre-sized silicon particles as stable battery anodes". Nature Energy. 1 (2): 15029. doi:10.1038/nenergy.2015.29. ISSN 2058-7546.
  7. ↑ "9 December 2014". Enevate Announces HD-Energy® Technology for Li-ion Batteries. Check date values in: |date= (help)
  8. ↑ Demerjian, Charlie (26 January 2016). "Enevate introduces a Silicon-Lithium-Ion battery".
  9. ↑ "Enevate Named as CES 2016 Innovation Awards Honoree in Multiple Categories". 12 February 2016.
  10. ↑ "Sonim picks Enevate batteries for ultra-rugged smartphones". 17 February 2016.
  11. ↑ Besenhard, J.; Daniel, C., eds. (2011). Handbook of Battery Materials. Wiley-VCH.
  12. ↑ Nazri, Gholam-Abbas; Pistoia, Gianfranco, eds. (2004). Lithium Batteries - Science and Technology. Kluwer Academic Publishers. p. 117. ISBN 1-4020-7628-2.
  13. ↑ Tarascon, J.M.; Armand, M. (2001). "Issues and challenges facing rechargeable lithium batteries". Nature. 414 (6861): 359–67. doi:10.1038/35104644. PMID 11713543.
  14. ↑ Berla, Lucas A.; Lee, Seok Woo; Ryu, Ill; Cui, Yi; Nix, William D. (2014). "Robustness of amorphous silicon during the initial lithiation/delithiation cycle". Journal of Power Sources. 258: 253. doi:10.1016/j.jpowsour.2014.02.032.
  15. ↑ Jung, H (2003). "Amorphous silicon anode for lithium-ion rechargeable batteries". Journal of Power Sources. 115 (2): 346. doi:10.1016/S0378-7753(02)00707-3.
  16. ↑ Chan, Candace K.; Peng, Hailin; Liu, Gao; McIlwrath, Kevin; Zhang, Xiao Feng; Huggins, Robert A.; Cui, Yi. "High-performance lithium battery anodes using silicon nanowires". Nature Nanotechnology. 3 (1): 31–35. doi:10.1038/nnano.2007.411.
  17. ↑ Ge, Mingyuan; Rong, Jiepeng; Fang, Xin; Zhang, Anyi; Lu, Yunhao; Zhou, Chongwu (2013-02-06). "Scalable preparation of porous silicon nanoparticles and their application for lithium-ion battery anodes". Nano Research. 6 (3): 174–181. doi:10.1007/s12274-013-0293-y. ISSN 1998-0124.
  18. ↑ Wu, Hui; Yu, Guihua; Pan, Lijia; Liu, Nian; McDowell, Matthew T.; Bao, Zhenan; Cui, Yi (2013-06-04). "Stable Li-ion battery anodes by in-situ polymerization of conducting hydrogel to conformally coat silicon nanoparticles". Nature Communications. 4. doi:10.1038/ncomms2941. ISSN 2041-1723.
  19. ↑ Higgins, Thomas M.; Park, Sang-Hoon; King, Paul J.; Zhang, Chuanfang (John); McEvoy, Niall; Berner, Nina C.; Daly, Dermot; Shmeliov, Aleksey; Khan, Umar (2016-03-22). "A Commercial Conducting Polymer as Both Binder and Conductive Additive for Silicon Nanoparticle-Based Lithium-Ion Battery Negative Electrodes". ACS Nano. 10 (3): 3702–3713. doi:10.1021/acsnano.6b00218. ISSN 1936-0851.
  20. 1 2 Chan, Candace K.; Ruffo, Riccardo; Hong, Seung Sae; Cui, Yi (2009). "Surface chemistry and morphology of the solid electrolyte interphase on silicon nanowire lithium-ion battery anodes". Journal of Power Sources. 189 (2): 1132–1140. doi:10.1016/j.jpowsour.2009.01.007. ISSN 0378-7753.
  21. ↑ Fong, Rosamaría (1990). "Studies of Lithium Intercalation into Carbons Using Nonaqueous Electrochemical Cells". Journal of The Electrochemical Society. 137 (7): 2009. doi:10.1149/1.2086855. ISSN 0013-4651.
  22. 1 2 Ruffo, Riccardo; Hong, Seung Sae; Chan, Candace K.; Huggins, Robert A.; Cui, Yi (2009). "Impedance Analysis of Silicon Nanowire Lithium Ion Battery Anodes". The Journal of Physical Chemistry C. 113 (26): 11390–11398. doi:10.1021/jp901594g. ISSN 1932-7447.
  23. 1 2 Oumellal, Y.; Delpuech, N.; Mazouzi, D.; Dupré, N.; Gaubicher, J.; Moreau, P.; Soudan, P.; Lestriez, B.; Guyomard, D. (2011). "The failure mechanism of nano-sized Si-based negative electrodes for lithium ion batteries". Journal of Materials Chemistry. 21 (17): 6201. doi:10.1039/c1jm10213c. ISSN 0959-9428.
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