In Situ Mechanistic Elucidation of Superior Si‐C‐Graphite Li‐Ion Battery Anode Formation with Thermal Safety Aspects

Abstract

understanding of the material synthesis/ fabrication, interfacial behavior, and thermal-chemical stabilities are vital. [3] With electronic appliances requiring stable voltage delivery, the current LIBs employ graphite or mixtures with soft carbons (carbon black) to achieve stable performance at discharge curves. [4] Since 1991, various forms of ordered and disordered (i.e., soft and hard) carbon have been primarily used as anode materials. [5] With graphitic carbon, a compromise was identified, which delivered a theoretical maximum capacity of 372 mAh g −1 , while maintaining stability and cycling characteristics. This stability comes at a cost of battery capacity, as it takes six carbon atoms to bind a single lithium ion (LiC 6 ) during charging process. [6] By contrast, alternative anode materials such as silicon, can bind about four lithium atoms (SiLi 4.4 ), improving energy densities by an order of magnitude. [7] Silicon anodes have garnered huge attention as they provide over ten times more theoretical capacity (3579 mAh g −1 ) than graphite anode. Problematically, the intercalated Si, Li 3.75 Si, swells in volume by about 320% during charging. Such huge volumetric expansion causes large material stresses, resulting in anode cracking, fracturing, loss of electrical contact (delamination), unstable solid electrolyte interface (SEI) and even catastrophic cell failure. [8][9][10][11] Naturally, this is unacceptable for practical and industrial applications. To overcome the capacity limitations of carbon, and the mechanical limitations of silicon, manufacturers have moved into composite materials-with the primary structure consisting of graphitic carbon, with silicon nanoparticles implanted within. First reported by Yoshio and co-workers in 2002, the C/Si composites did improve capacity, but the silicon nanoparticles were difficult to merge with the carbon bulk. [12,13] After repeated cycling, it was found that the particles separate and capacity drops. [14] Li et al. reported fabrication of graphite-Si composite using polymer blends of poly(diallyl dimethyl-ammonium chloride) and poly(sodium 4-styrenesulfonate) to obtain capacity of 450 mAh g −1 with 95% capacity retention after 200 cycles. [15] Zhang et al. prepared core-shell structure (Si@C) using silicon nanoparticles (Si-NPs) and emulsion polymerization of acrylonitrile, followed by pyrolysis. [16] The composite [15] retained A composite anode material synthesized using silicon nanoparticles, micrometer sized graphite particles, and starch-derived amorphous carbon (GCSi) offers scalability and enhanced electrochemical performance when compared to existing graphite anodes. Mechanistic elucidation of the formation steps of tailored GCSi composite are achieved with environmental transmission electron microscopy (ETEM) and thermal safety aspects of the composite anode are studied for the first time using specially designed multimode calorimetry for coin cell studies. Electrochemical analysis of the composite anode demonstrates a high initial discharge capaci...

In Situ Replenishment of Formation Cycle Lithium‐Ion Loss for Enhancing Battery Life

“…It delivered stable discharge-charge capacities of 628/600 mAh g −1 for 3rd cycle (Figure 4b). The yielded capacities of C-Si material were almost closer to the Li versus C-Si half-cell results discharge-charge capacities of 641/627 mAh g −1 (40th cycle) at 0.1 C between 0.01and 2.0 V, [26,45] as shown in Figure S13 in the Supporting Information and higher than the Li versus MCMB half-cell results, discharge-charge capacities 390/388 mAh g −1 (75th cycle) at 0.1 C between 0.01 and 1.5 V as shown in Figure S7 in the Supporting Information, for the reason of Si contribution during alloying and dealloying reaction.…”

“…All the diffraction peaks of MCMB and LiFePO 4 are well indexed with standard patterns JCPDS# 00‐008‐0415 (indicated in red for MCMB) [ 44 ] and JCPDS# 00‐040‐1499 (indicated in pink for LiFePO 4 ), [ 17 ] and confirmed that no other impurity phase was present (Figure 1f). Similarly, the C–Si anode (purple) and LiNi 1/3 Mn 1/3 Co 1/3 O 2 cathode (brown) materials were compared with the standard XRD patterns of C, JCPDS# 00‐008‐0415 (orange) [ 32,45 ] and Si, JCPDS# 01‐089‐2749 (cyan) [ 32,45 ] and LiNi 1/3 Mn 1/3 Co 1/3 O 2 , JCPDS# 01‐087‐1564 (violet) [ 28,46 ] as shown in Figure 1g. All the inset FESEM images are associated with the respective electrode material morphology, given in Figure S1 in the Supporting Information.…”

“…From these obtained results, our proposed hypothesis of direct in situ SEI formation on C-Si anode prevents the further Li + ion loss during C-Si versus LiNi 1/3 Mn 1/3 Co 1/3 O 2 cycling in SLLIB. Also, the flat-voltage profile of C-Si anode [26,45] and slop-voltage profile of LiNi 1/3 Mn 1/3 Co 1/3 O 2 cathode [28,46] were corroborated with the oxidation and reduction peaks at 0.20/0.02 V and 0.49/0.16 V for C-Si anode [33,45] ( Figure S15a, Supporting Information) and 3.90/3.65 V for LiNi 1/3 Mn 1/3 Co 1/3 O 2 cathode [28,46] ( Figure S15b anode ). Indeed, the delivered charge-discharge capacities of 186/171 mAh g −1 for SLLIB-C-Si versus LiNi 1/3 Mn 1/3 Co 1/3 O 2 were higher than the conventional full-cell (C-Si vs LiNi 1/3 Mn 1/3 Co 1/3 O 2 ) charge-discharge capacities of 158/137 mAh g −1 (Figure 4d) and reached closer to LiNi 1/3 Mn 1/3 Co 1/3 O 2 half-cell results 165/163 mAh g −1 at 0.2 C ( Figure S14, Supporting Information) for the 2nd cycle.…”

Nickel-Embedded Carbon Materials Derived from Wheat Flour for Li-Ion Storage

“…The carbon originated from wheat flour delivered a good specific capacity of 390 mAh g −1 at 1C with a good rate and cycle performance for LIBs [ 28 ]. The wheat flour-based carbon materials have been used as various kinds of electrode materials for supercapacitors and other batteries recently [ 27 , 29 , 30 , 31 , 32 ]. Recently, metal and metallic oxide encapsulated into porous carbon is considered to be a simple method to obtain composite with good electrochemical property, such as Sb/C composite [ 33 ], MnO/metal/carbon nanohybrid [ 34 ], CuO/C [ 35 ].…”

An alternative means of advanced energy storage by electrochemical modification

“…To solve these issues, the major focus has been on material engineering by nanotechnology. Through morphology control and nanostructuring, many novel active materials have showed promising electrochemical performance in a laboratory cell [6][7][8][9][10]. However, nanotechnology that is cost-effective and can be used on an industrial scale is still lacking.…”