Advances in Direct Recycling of Lithium-Ion Electrode Materials
Authors: Sloop Steven E , Trevey James E , Gaines Linda 
Published: February 2020

This paper describes performance capabilities of nickel-rich LiNixMnyCozO2 lithium-ion chemistries after Direct Recycling, which is a method to reinstate structure/property relationships in worn/failed electrodes. It includes comparative analyses of treated NMCs (T-NMCs) and pristine NMCs after Direct Recycling. The vertical integration of Direct Recycling into battery manufacturing will significantly reduce material costs and address long term economic sustainability for the battery industry.

Current lithium-ion cathode production exceeds $2B. Market projections indicate this will top $7.3B by 2025 [1]. Recycling does not significantly contribute to cathode production; but a modest use of 5% recycled cathode by 2025 has a potential value in excess of $370M. Challenges for lithium-ion recycling include:

(1) Fees for end-of-life recycling or disposition.

(2) Loss of critical material in low recycling yields.

(3) Low grade material from recycling.

Hydrometallurgic or pyrometallurgic refining technologies are the main approaches for recycling; these aim for cobalt and nickel recovery. The energy investment in original manufacturing of cathode structures is lost with these processes. On the other hand, Direct Recycling offers a feasible way to conserve that energy-input independently of cobalt/nickel content [2-3].

Other workers have developed Direct Recycling using painstaking stoichiometric methods to reinstate lithium-metal-oxide ratios [4]. OnTo’s processes refurbish the cathode materials, using simple methods without extensive elemental analyses; examples include reintroduction of lithium into spent electrode materials taught in US patents referenced below [5-6]. These methods also remove trace metals from >75ppm to 12ppm. Such high purity has the potential to improve performance of reclaimed material over original (i.e. longer cycle life). Direct Recycled, EV grade NMC electrodes (R-NMC) demonstrate 2,500 cycles, low self-discharge and performance equal to original NMC; with a cost of 1/3rd of the original manufacture. Processing spent batteries includes production of shredder residue (sometime referred to as black-mass in the recycling industry). Separation of solid oxide electrode materials from binders, carbon black and graphite is a feature that is a simultaneous part of Direct Recycling.

Aqueous methods can be used in these process. One challenge is the dissolution of metals from the oxide particles. This paper demonstrates the control/minimization of dissolution while improving the lithium capacity in the (used) lattice system. This paper outlines Direct Recycle feasibility on a suite of lithium-ion chemistries including nickel rich NMC, spinel lithium manganese oxide (LMO) mixed with NMC, lithium-iron phosphate (LFP), and lithium cobalt oxide (LCO) from early prototypical formulations to the modern, high capacity versions.

This work investigates Direct Recycling on NMC and T-NMCs. New samples of each electrode were allowed to stand in air to degrade capacity. As a result of Direct Recycle processing, the specific capacity of T-NMC rebounded from 140 to 175mAh/g; while similarly processed uncoated NMC rebounded from 90 to 140 mAh/g.

These processes are designed to address failure mechanisms exhibited during life cycling and storage of NMC chemistries, such as the Ni2+ accumulation in the surface regions of electrodes. One feature is they oxidize surface nickel ions as shown in the comparison (below) of used and treated electrode particles with XPS. Specifically, the Ni 3p signal diminishes indicating the drop in concentration of Ni2+ at the particle surface after processing.

References

Pillot, C. Proceedings of The International Battery Seminar and Exhibit

IBSE 2015
Ft. Lauderdale, FL March 16, 2015.

Dunn, J.B.; Gaines, L. ; Sullivan, J.; Wang, M.Q. Environ. Sci. Technol. “Impact of recycling on cradle-to-gate energy consumption and greenhouse gas emissions of automotive lithium-ion batteries” 46 (22), 12704-12710, (2012)

Gaines, L. Sloop, S.; “EV Battery Recycling Technology: Challenges and Opportunities”
IBSE 2016
Ft. Lauderdale, FL, March 21, 2016.

Mathew, S.; Menon, K.; Scordilis-Kelly, C.; Saidi M.Y. “Method for Recovering Particulate Material from Electrical Components” U. S. Patent # 6,150,050.

Sloop, S. “Reintroduction of lithium into recycled battery materials” U. S. Patent # 8,846,225.

Sloop, S. “Reintroduction of lithium into recycled battery materials” U.S. Patent # 9,287,552

Keywords: lithium-ion manufacture; recycle; critical materials; direct recycling; atomic layer deposition; failure modes.

Figure 1