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Positive Electrode Formulation for Silicon Based Negative Electrodes

IP.com Disclosure Number: IPCOM000248483D
Publication Date: 2016-Dec-06
Document File: 6 page(s) / 398K

Publishing Venue

The IP.com Prior Art Database

Abstract

his paper describes blended positive active materials for use in lithium ion batteries using silicon and silicon alloys. These formulations provide a wide operating voltage range of the positive electrode and demonstrate improved cycle performance in test cells.

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Positive Electrode Formulation for Silicon Based Negative Electrodes

This paper describes blended positive active materials for use in lithium ion batteries using silicon and silicon alloys. These formulations provide a wide operating voltage range of the positive electrode and demonstrate improved cycle performance in test cells.

Background & Description

Silicon based alloys are commonly known as the next generation of high density materials for negative electrodes of lithium ion batteries. However, these alloys may undergo large volume changes during lithiation and de-lithiation.

The approach of this paper is to control the voltage of the negative Si-alloy electrode by varying the composition of the positive electrode. The volume change of the Si-alloy electrode is related to its operating voltage range, and can be reduced as long as the operating voltage range is controlled. The lithiation capacity distribution of the positive electrode is a key factor in controlling the voltage of negative electrode. Many compositions of positive electrode materials can used, including LCO, nickel metal carbide NMC, LMO, NCA, and LFP. This paper proposes that these materials can be blended to form new positive electrode materials. Alternatively, new positive electrodes can be created by coating one or more of these materials on the surface of another material.

High Voltage LCO has a good lithiation capacity distribution between 3.7V and 4.4V, and provides a high volume density for positive electrodes. However, this material does not provide much capacity at lower voltages (e.g., between 3.0V and 3.7V), and it increases the maximum voltage of the Si-alloy electrode in full cell systems. The voltage affects to large volume exchanging of Si-alloy and cannot make good cycle performance on it. NMC622 positive electrodes, on the other hand, demonstrate a good lithiation capacity distribution between 3.0V and 4.2V, and tend to suppress the increase in the maximum voltage of the Si-alloy electrode. As a result, NMC622 electrodes can control large volume changes, and yield good cycle performance. However, NMC622 cannot provide high volume density of positive electrode, and exhibits poor performance at high voltages in comparison to High Voltage LCO. Hence this paper proposes using positive electrodes made from a blend of materials, in order to provide good lithiation capacity distribution over wide operating ranges. In particular, blends of High Voltage LCO and LaPO4 coated NMC622 are described.

Experimental

The final formulations of positive electrode Examples 1-6 are provided in Table 1.


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Table 1: Electrode Formulations of Examples

Example 1:

The positive electrode was prepared by milling to disperse of conductors and Si-alloy materials in NMP solvent. 5.0g of ECP and 14.0g of Kynar460 were placed in a 2L bottle with zirconia balls and mixed at 5rpm for 10 min. 350.0g of NMP solvent was added to the mixture in the bottle and mixed at 25...