1. Introduction
Fast economic development and huge energy consumption
have spawned rapid decrease of fossil fuels along with large
emission of CO2. To sustain the non-renewable resources and
reduce CO2 emission, the only way out is to develop new
energy. The great harvest of recent investigations on new energy
is inspiring, and will accelerate the transformation of
fossil fuel based economy to clean energy economy [1e3].
Batteries, whose capacity to efficiently convert and store
electrical energy was recognized early on, have been used in a
myriad of applications extending from portable electronic
devices and grid-scale energy storage to electric vehicles
(EVs) [4e6]. Among all kinds of batteries so far, lithium-ion
batteries have captured the market due to high gravimetric and
volumetric capacity as well as good energy efficiency [1].