Font Size

HOME > No.19, Nov 2019 > Progress Towards the Realisation of Advanced Higher Capacity Li-ion Batteries

Progress Towards the Realisation of Advanced Higher Capacity Li-ion Batteries

Binder-less tin phosphide/carbon composite film electrodes by aerosol deposition processBy Ryoji Inada
Associate Professor Ryoji Inada (Center) and his students

Associate Professor Ryoji Inada and his research team at the Toyohashi University of Technology have successfully fabricated a binder-less tin phosphide (Sn4P3)/carbon (C) composite film electrode for lithium-ion batteries via aerosol deposition. The Sn4P3/C particles were directly solidified on a metal substrate via impact consolidation, without applying a binder. Charging and discharging cycling stabilities were improved by both complexed carbon and a controlled electrical potential window for lithium extraction. This new material could help realize advanced lithium-ion batteries of higher capacity.

Lithium-ion (Li-ion) batteries are widely used as a power source in portable electronic devices. They have recently attracted considerable attention because of their potential to be employed in large-scale uses, such as acting as a power source for electric vehicles and plugin hybrid electric vehicles, and as a stationary energy storage system for renewable energy. To realize advanced Li-ion batteries with higher energy density, anode materials with higher capacity are required. Although a few Li alloys such as Li–Si and Li–Sn, whose theoretical capacity is much higher than that of graphite (theoretical gravimetric capacity = 372 mAh/g), have been extensively studied, they generally result in poor cycling stability due to the large variation in volume during charging and discharging reactions.

Fig.1 Scanning electron microscope (SEM) images of Sn4P3/C composite particles (1st row:1st image), and surface of Sn4P3/C composite film fabricated by the AD process (1st row:3rd image). Corresponding elementary distributions for Sn, P, and C are also shown.

Tin phosphide (Sn4P3) (theoretical gravimetric capacity = 1255 mAh/g) with layered structure, generally used as a high-capacity alloy-based anode material for Li-ion batteries, has an averaged operational potential of ~0.5 V vs. Li/Li+. Reports indicate that complexing carbon materials with nano-structured Sn4P3 particles significantly enhance the cycling stability. Generally, electrodes used in batteries are fabricated by coating a slurry consisting of electrode active materials, conductive carbon additives, and binders, on metallic foils. For carbon complexed Sn4P3 (Sn4P3/C) anodes (such as those reported in the literature), the weight fraction of the active materials in an electrode is decreased by approximately 60~70 % because of the use of significant quantities of conductive additives and binders to achieve stable cycling. Consequently, the gravimetric specific capacity per electrode weight (including those of conductive carbon additives and binders) is decreased significantly.

Fig.2 Cycling performance of Sn4P3 and Sn4P3/C composite films for different carbon contents (left) in a two-electrode cell with Li metal as the counter electrode. Cycling test was performed at cell voltage windows ranging from 0 V to 2.5 V. SEM images of Sn4P3/C composite film surface after the 1st (middle) and 100th cycles (right) are also shown.

Associate Professor Ryoji Inada and his research team at the Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, have successfully fabricated a binder-less Sn4P3/C composite film electrode for Li-ion battery anodes via aerosol deposition (AD). In this process, the Sn4P3 particles are complexed with acetylene black using a simple ball-milling method; the obtained Sn4P3/C particles are then directly solidified on a metal substrate via impact consolidation without adding any other conductive additives or binders.

This method enables enhancement of the fraction of Sn4P3 in the composite to above 80%. Furthermore, structural change of the composite electrode is reduced and cycling stability is improved by both complexed carbon and a controlled electrical potential window for lithium extraction reaction. The Sn4P3/C composite film fabricated by the AD process maintains gravimetric capacities of approximately 730 mAh g-1, 500 mAh g-1, and 400 mAh g-1 at 100th, 200th, and 400th cycles, respectively.

The first author Toki Moritaka is quoted as saying, "Although optimizing the deposition conditions was difficult, useful information on enhancement of cycling stability of the Sn4P3/C composite film electrode fabricated by the AD process was obtained. The complexed carbon functions not only as a buffer to suppress the collapse of electrodes caused by the large variation in the volume of Sn4P3, but also as an electronic conduction path among the atomized active material particles in the composite."

"This process is an effective means to increase the capacity value per electrode weight. We believe there is scope for improvement of the electrochemical performance by the size and content of the carbon in Sn4P3/C used in composite film fabrication by the AD process. We are now trying to optimize the complexed carbon content and increase the composite film thickness," quotes Associate Professor Ryoji Inada.

Fig.3 Long-term cycling performance of Sn4P3/C composite films at different cell voltage windows ranging from 0 V to 0.75 V, and that from 1 V and to 1.25 V (left). SEM images of Sn4P3/C composite film surfaces cycled at 0 V0.75 V (middle) and that at 0 V1.25 V (right) are also shown.

The findings of this study may contribute to the realization of advanced Li-ion batteries of higher capacity. Moreover, because not only Li but Na can also be stored in and extracted from Sn4P3 by similar alloying and dealloying reactions, the Sn4P3 electrode can be employed in next-generation Na-ion batteries at much lower costs.

This work was partly supported by Grant-in-Aids for Scientific Research (Grant No. 16K06218 and 16KK0127) from the Japan Society for the Promotion of Science (JSPS).


Toki Moritaka, Yuh Yamashita, Tomohiro Tojo. Ryoji Inada, Yoji Sakurai (2019). Characterization of Sn4P3–Carbon Composite Films for Lithium-Ion Battery Anode Fabricated by Aerosol Deposition: Nanomaterials, 9(7), 1032.10.3390/nano9071032.


By 稲田 亮史

豊橋技術科学大学の研究グループは、エアロゾル・デポジション(AD)法を用いてバインダ(結着材)を用いず、リン化錫(Sn4P3)/ カーボン(C)複合膜を金属基板上に形成することに成功しました。原料であるSn4P3/C粒子が基板に衝突した際の衝撃により変形・固化することにより、複合膜が形成できたと考えられます。カーボン複合化とリチウム脱離反応時の電圧の制御を組み合わせることで、充放電サイクル特性が向上することを確認しました。本成果は、次世代型高容量リチウムイオン電池の実現に貢献すると考えられます。


リン化錫Sn4P3(理論容量:1255mAh/g)は、リチウム基準で約0.5 Vの電位で作動する高容量合金系負極材料の一つです。ナノサイズ化したSn4P3をカーボン(C)と複合化することで、そのサイクル安定性が向上することが既に確認されています。一般的にリチウムイオン電池の電極は、充放電を担う材料(活物質)と導電助剤、バインダ(結着材)および溶剤を混合してスラリーを作製し、これを金属箔上に塗布・乾燥する工程で作製されます。Sn4P3/C複合粒子を活物質とした先行研究では、サイクル安定性向上のため多量の導電助剤・バインダを混合しており、最終的な電極内での活物質の充填率(重量)は60~70%となり、電極総重量あたりの容量値が低下するという課題があります。






Share this story

Researcher Profile

Tomoaki Mashimo
Name Ryoji Inada
Affiliation Department of Electrical and Electronic Information Engineering
Title Associate Professor
Fields of Research Energy Conversion Engineering / Electirical and Electronic Material Engineering / Electrochemistry