Large storage solid-state Li-ion batteries

Introduction

To make batteries suitable for electric cars or home storage, imec is developing solid state electrolytes with high conductivity (>1E-2 S/cm) to increase the energy capacity of solid state Li-ion batteries. Imec’s solid electrolyte is fully compatible with existing Li-ion battery fabrication tools as the electrolyte is applied via a liquid precursor and solidified once applied. In this way, Imec’s approach distinguishes from the typical inorganic solid powder electrolytes which needs new fabrication schemes.

High conductivity electrolyte

Imec is engineering materials at the nanoscale to develop an (inorganic) nano-composite electrolyte with high ion conductivities larger than 1E-2 S/cm and with a large electrochemical stability window (0V – 5V vs. Li⁺/Li).

We design solid electrolytes through the principle of heterogeneous doping.  Heterogeneous doping refers to the significantly enhanced ion transport that occurs at the interface between an oxide insulator (e.g. silica or alumina) and a salt electrolyte. This interface phenomena is exploited to create new Li-ion electrolyte materials with high ionic conductivity. The concept of using interfaces to engineer ion conductivity is termed “nanoionics”.

We use, for example, nanoporous silica, a material that we have a great deal of experience with in the chip industry. When combined with a lithium salt into a composite, faster ion conduction can be achieved as the lithium ions move through this material along the internal surface of the silica.

We have demonstrated nanocomposite electrolytes with ion conductivities exceeding several mS/cm at room temperature.

Embedded nanocomposite electrolyte

Using this high conductivity electrolyte, imec is developing a high capacity solid-state powder battery. Imec’s solid electrolyte is applied via a liquid precursor and solidified once inside the powder electrodes. As such, high density electrodes with high capacity are made.

Battery performance and reliability (life-time) are determined by the control of interfaces. If an interface is blocked, that part of the battery won’t work anymore. Imec is developing protective coatings with dually ionic and electronic conducting properties.

To increase the capacity to the order of Ah (ampere hours), imec is developing thick (>100 micrometers) electrode structures.

This work is part of EnergyVille, a center of expertise that unites KU Leuven, VITO, Hasselt University and imec for research into sustainable energy and intelligent energy systems.

Applications

Large storage systems for:

• portable electronics (such as laptops or cameras)
• electric cars
• home storage systems for the smart grid
• future smart house-hold appliances and autonomous robots