Printed Planar Lithium Ion Batteries
Authors: Hsieh Bing R 
Published: February 2020

There continues to be a need to increase the energy density of lithium-ion ion batteries for a wide range of applications, including portable devices, electric vehicles, and grid storage. From 1995 to 2014, energy density grew at an annual pace of only 6%, while the demand for energy storage has grown at a far faster pace. For example, an iPhone® 6 introduced in 2014 is about 50 times faster than the first iPhone® introduced in 2007, yet the energy density of commonly-used batteries has grown by only about 30% over the same period. In order to satisfy the demands for yet higher energy densities, advanced electrochemically active materials are being developed, including the development of cathodes that use sulfur and oxygen and silicon and lithium metal for the anodes. These newer generations of Li ion battery materials promise to deliver energy densities of more than 800Wh/kg, about a 2X improvement. In addition to developing advanced battery materials, new battery architectures are being developed, such as batteries that have 3D structures [1]. Nevertheless, the fabrication of 3D structures has been extremely complicated. Mass production of 3D cells has been cost prohibitive, especially for large scale application such as EV and grid storage. As a result, their applications have been limited to micro-batteries. Therefore, what is needed is a novel battery design suitable for large format batteries, which can be manufactured easily and cost-effectively.
Recently, we filed a patent application disclosing several new planar battery designs comprising a planar microbattery cell array, as shown below [2]. The array includes a plurality of devices arranged parallel to one another on a substrate. Each device has a positive electrode (dotted areas) and a positive current collector layer (gray areas) that is in contact with at least a portion of a first sidewall of the positive electrode and optionally some or all of the top surface of the positive electrode. Similarly, each device also has a negative electrode (hatched areas) parallel to the positive electrode and a negative current collector layer. There is also an electrolyte in contact with both the positive electrodes and the negative electrodes (not shown). Within the plurality of devices, the positive electrode current collector layer has a first comb structure, and the negative electrode current collector layer has a second comb structure, and the first comb structure and the second comb structure are arranged in an interdigitated configuration. In this presentation we will discuss the design considerations of such planar battery structures, their corresponding pack designs, as well as their low cost fabrication methods involving printing processes.
1. (a) Ning, H, et al., Proc. Natl. Acad. Sci. 2015, 112, 6573-6578; (b) Pikul, JH, et al. Nat. Commun. 2013, 4:1732 doi: 10.1038/ncomms2747; (c) Sun, K, et al. Adv. Mater. 2013, 25, 4539; (d) Oudenhoven, JFM, et al. Adv. Energy Mater. 2011, 1, 10-33; (e) Arthur, TS, et al. MRS Bulletin 2011, 36, 523-531; (f) Long, JW, et al. 2004, Chem. Rev. 104, 4463–4492.
2. Hsieh, BR US patent application filed in April 2017

Figure 1