锂离子电池Science-Building a Better Battery-Chiang-1485-6

独 创 性
large volume changes associated with the charge-discharge cycle. On page 1515 of this issue, Huang et al. (1) report an ingenious in situ transmission electron microscope (TEM)
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Building a Better Battery Yet-Ming Chiang Science 330, 1485 (2010); DOI: 10.1126/science.1198591
ously meet to be commercialized. One route of these issues need to be convincingly and
by which battery performance can be com- simultaneously addressed if laboratory-based
Controlling the charge-induced morphological changes of electrode materials may provide a route to improved battery performance.
Li2O or LiF that does react reversibly with the metal electrode and is the main contributor to reversible capacity (2, 4). However, the large strain accommodation capability shown by the SnO2 nanowires would be valuable if achievable in other high-capacity, high-strain electrodes such as silicon. Alloying with Li to the limiting composition Li4.4Si yields theoretically an enormous capacity of 4200 milliampere hours per gram (mAh/g), versus 150 mAh/g for LiCoO2 cathodes and 350 mAh/g for graphite anodes used in conventional lithium-ion batteries, but also produces a molar volume change of 311%. Silicon undergoes solid-state amorphization during lithiation
is a most important metric (e.g., electric vehicle and grid storage batteries); and nanoscale forms of inherently reactive compounds raise
主张
early 1990s. Thus, in the burgeoning field of nanoscale electrode materials, skepticism
PERSPECTIVES
MATERIALS SCIENCE
Building a Better Battery
Yet-Ming Chiang
新方法，新事物
不常见的
Innovations in the battery field are infrequent and hard-won. New electrochemical systems (a new positive or nega-
prising because of the many requirements storage because of departures from known
that any battery electrode must simultane- scaling laws as the size scale decreases. All
怀疑 tive electrode, electrolyte, or combination
cerns specific to nanomaterials: Nanoparticle electrodes may have low packing density that makes high bulk energy density difficult to realize; synthesis methods may not be scal-
experiment that uses a low–vapor pressure intercalation reactions are realized with dis- morphology; diffuse phase boundaries migrate inward
ionic liquid electrolyte to allow imaging of a placement or “conversion” reactions that pro- along the [010] direction. CLi, lithium concentration SnO2 nanowire electrode in an “open” elec- duce one or more new phases. Electrochemitrochemical cell. They observe a reaction cal reduction of the starting oxide by lithium (6), and one strategy for strain accommoda-
substantial progress in battery performance. SnO2 is a model for a class of metal oxides
and fluorides (2–4) in which reversible storage capacities exceeding those possible with
that under a moderate overpotential of 25 mV, misfit stress causes FePO4 to grow along the [100] longitudinal direction, normal to the fast-diffusion direction. (B) Increasing the overpotential to 100 mV allows Li diffusion anisotropy to dominate the ach the marketplace only once able and/or economical in a field where cost
怀疑 主义
every few years, and the energy density of lithium-ion batteries as a class has increased on average by only 8 to 9% per year since the
Science (print ISSN 0036-8075; online ISSN 1095-9203) is published weekly, except the last week in December, by the American Association for the Advancement of Science, 1200 New York Avenue NW, Washington, DC 20005. Copyright 2010 by the American Association for the Advancement of Science; all rights reserved. The title Science is a registered trademark of AAAS.
FePO4
0
A
LiFePO4
妥协，折中
B
promised is by mechanical failure due to the results are to be successfully translated into Coping with strain. (A) Phase field modeling reveals
CREDIT: MING TANG/LAWRENCE/LIVERMORE NATIONAL LABORATORY
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[100] [001] [010]
1
Fast Li diffusivity
0.5 CLi
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