解决锂离子电池硅碳负极问题的策略

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"这篇研究论文探讨了锂离子电池中硅碳负极材料所面临的问题，并提出了相应的解决方案。作者包括Xuyan Liu、Xinjie Zhu和Deng Pan，来自上海科技大学机械工程学院。文章经过皇家学会的编辑、同行评审和接受流程。" 锂离子电池在各种行业中广泛应用，如便携式电子设备、移动电话和新能源汽车电池等，展现出巨大的潜力。然而，随着对更高能量密度和更长寿命电池的需求增加，硅碳（Si-C）复合材料作为锂离子电池负极的研究越来越受到关注。硅碳负极因其高理论比容量（约4200mAh/g）而被看作是取代传统石墨负极的理想选择。但硅在锂化过程中体积变化大（高达300%），这导致了电极结构的破坏，缩短了电池的循环寿命。论文中，作者详细分析了硅碳负极材料存在的主要问题，包括： 1. **体积膨胀与收缩**：在充放电过程中，硅会经历显著的体积变化，这导致电极粒子间的机械断裂，形成内部裂纹，从而增加了内阻并降低了电化学性能。 2. **电解质界面膜的形成**：在首次充电时，硅表面会与电解质反应生成固态电解质界面膜（SEI），这会消耗大量的锂，降低首次库仑效率，并可能导致持续的SEI生长，进一步影响电池性能。 3. **颗粒破碎**：由于反复的体积变化，硅颗粒可能会破碎，这使得它们更容易从集流体上脱落，进一步恶化电池的循环稳定性。针对这些问题，论文提出了以下解决方案： 1. **纳米化与复合材料设计**：通过将硅制成纳米颗粒或将其与其他材料（如碳、金属氧化物）复合，可以缓解体积变化带来的应力，提高结构稳定性。 2. **多孔结构设计**：利用三维多孔骨架结构，可以为体积变化提供缓冲空间，减少颗粒间的相互作用，降低机械压力。 3. **表面改性**：通过表面包覆、预锂化或其他化学修饰方法，可以改善SEI的质量，减少电解质的消耗，提高首次循环效率。 4. **结构增强剂的使用**：引入聚合物、导电网络或其他弹性材料，可以增强电极的机械强度，防止颗粒在循环过程中的破碎。 5. **优化电解液配方**：选用适当的电解质添加剂或新型电解质，可以改善SEI膜的性质，降低副反应，提高电池的循环稳定性和库仑效率。这篇研究论文深入探讨了硅碳负极材料在锂离子电池中的挑战，并提出了一系列创新策略以克服这些问题，为未来高能量密度电池的设计提供了重要参考。通过不断的技术改进和新材料的研发，硅碳负极有望实现商业化的广泛应用，推动锂离子电池技术的进一步发展。

rsos.royalsocietypublishing.org R. Soc. open sci. 5:172370

................................................

carbon nanofibre

SiH

CVD

a-Si shell

stainless steel substrates

(b)(a)

Figure 1. Schematic illustration of Si coating onto carbon nanobres. (a)BareCNFs.(b) C–Si core–shell NWs [36].

3.1.2. Silicon–carbon nanobres

The attractive properties of catalytically grown carbon nanoﬁbres (CNFs) have been known for decades

[50]. They can be mass-produced inexpensively, and have excellent mechanical strength and high thermal

and electrical conductivity [51]. The hybrid nanostructured Si/CNFs anodes exhibited superior device

performance to that of materials used in previous studies, in terms of both speciﬁc capacity and cycle

life. The CNFs provide not only a good strain/stress relaxation layer but also a conductive electron

pathway [52].

Shu et al.[38] developed hollow carbon nanoﬁbres/Si composites by a facile CVD technique with

iron nitrate as the catalyst source and acetylene as the carbon source. They show excellent rate

capability as anode materials for lithium batteries. The initial discharge and charge capacities of the

CNFs/Si composites at 0.60 C are 1197.8 and 941.4 mAh g

−1

, respectively. A reversible charge capacity

of 733.9 mAh g

−1

can be delivered at 0.60 C after twenty cycles and the capacity retention is as high as

77.9%. It is found that CNFs/Si composites show superior electrochemical properties as anode materials

for lithium batteries. They not only provide electronic conducting bridges between Si particles and the

current collector for electron transportation but also act as a buffer to suppress the volume expansion of

Si particles during lithiation and delithiation reactions.

A novel ﬂexible three-dimensional (3-D) Si/C ﬁbre paper electrode [39] is synthesized by

simultaneously electrospraying nano-Si-PAN (polyacrylonitrile) clusters and electrospinning PAN ﬁbres

followed by carbonization. The ﬂexible 3-D Si/C ﬁbre paper electrode demonstrate a very high overall

capacity of about 1600 mAh g

−1

with capacity loss less than 0.079% per cycle for 600 cycles and excellent

rate capability. Wang and co-workers [40] developed a new porous composite nanoﬁbres manufacturing

route, combining electrospinning and foaming processes (illustrated in ﬁgure 2). After 20 cycles ,when all

these batteries reach stable charging/discharging rate, the discharging capacity shows as 1045 mAh g

−1

for porous C/Si/AACA composite nanoﬁbres. Kim et al.[41] introduced a 3-D paper-type Si–carbon

nanoﬁbre-composite electrode (Si/CNF–P) as a binder/current collector-free anode for LIBs that was

prepared using an electrospinning method. Figure 3 shows Nyquist plots of the electrodes after the

1st, 5th and 100th cycles. Si–NP and Si/CNF–G exhibited a sharp deterioration in the discharge

capacity, which might be due to a serious volumetric expansion by the alloy/dealloy process during

the cycling. However, the Si/CNF–P exhibited a high initial capacity of 1957 mAh g

−1

at 2 A g

−1

and

maintained 1187 mAh g

−1

(retention rate of 60.6%) for 400 cycles. The enhanced cycling performance of

Si/CNF–P might result from the suppression of the volumetric expansion of Si and facilitation of Li-ion

transport. Si–NP and Si/CNF–G showed a severe increment of the charge transfer resistance (R

) due

to increased interface resistance after the cycling process, whereas Si/CNF–P showed a relatively slight

increment of R

due to the stable electrode structure containing Si on CNF with voids, which could

effectively release the volumetric expansion. These results conﬁrm that the combination of CNFs and Si

dramatically improves the electric conductivity and reduces the total cell resistance, which leads to the

good performance of Si/CNF nanocomposite electrodes.

3.1.3. Silicon–carbon nanotubes

Among all the conducting carbon materials, the carbon nanotube (CNT) is a one-dimensional material

with a hollow tube including a curled graphene structure and an end cap with a hemispherical fullerene

structure. CNTs, an allotrope of graphite, have been reported to show much improved lithium storage

capacity compared with graphite, because of their unique structures and properties. CNTs have been

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