Electrode Active Material with Multilayer Carbon Buffering
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Solution Overview
Problem
Lithium secondary batteries using metal-based electrode active materials suffer from rapid capacity drop and poor cycle life due to severe volume changes during charge/discharge cycles, which existing materials fail to adequately address.
Innovation Solution
An electrode active material comprising a core layer of metals like Si, Al, with an amorphous carbon layer and a crystalline carbon layer, where the crystalline carbon layer is formed of sheet-like units in a multilayer structure to buffer volume variations, inhibiting core layer expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metal-based electrode active materials (Si, Al, etc.) are used to achieve higher charge/discharge capacity, then capacity is improved, but severe volume change occurs during lithium intercalation/deintercalation causing cracking and rapid capacity drop
Solution Approach 1:
The core layer (metal or metalloid) is nested within the amorphous carbon layer, which is in turn nested within the crystalline carbon layer. This nested structure allows the core material to expand and contract during lithium intercalation/deintercalation while being constrained and protected by the carbon layers, preventing cracking and maintaining structural integrity over multiple cycles.
Solution Approach 2:
The invention uses a composite structure combining metal/metalloid core material with amorphous carbon and crystalline carbon layers. This composite material approach allows the high-capacity metal core to be protected by the carbon layers that accommodate volume changes, achieving both high capacity and good cycle life characteristics.
2Quantity of substance
If metal-based electrode active materials are used to achieve higher capacity, then capacity is improved, but the materials crack and divide due to volume changes, worsening structural stability
Solution Approach 1:
The amorphous carbon layer and crystalline carbon layer act as flexible shells surrounding the core material. These carbon layers can accommodate volume expansion and contraction during charge/discharge cycles without cracking, thereby protecting the core material and maintaining structural stability.
Solution Approach 2:
The carbon layers are formed beforehand to surround and protect the core material before any volume changes occur during cycling. This pre-formed protective structure cushions the core material against the stresses of expansion and contraction, preventing cracking and structural degradation.
3Ease of manufacture
If conventional electrode active materials are used, then manufacturing is simpler, but they cannot provide excellent cycle life characteristics and are insufficient for practical applications
Solution Approach 1:
The invention changes the structural parameters of the electrode material by forming a multi-layer structure with specific thickness ratios (core layer: amorphous carbon layer: crystalline carbon layer = 70-30: 0.1-50: 29.9-70). This parameter optimization achieves excellent cycle life characteristics while maintaining practical manufacturability through established coating and heat treatment processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The electrode active material with a multilayer crystalline carbon layer effectively stabilizes the core layer, maintaining high charge/discharge capacity and cycle life characteristics by buffering volume changes, resulting in improved battery performance.
Implementation Method 1
the crystalline carbon layer, which is formed of sheet-like carbon layer units and is partially or totally formed of bilayer or multilayer sheet-like carbon layer units, so as to inhibit variations in volume of the core layer
Implementation Method 2
a lithium secondary battery generates electric energy via redox reactions induced by the lithium ion intercalation/deintercalation at the cathode and the anode
Implementation Method 3
a lithium secondary battery generates electric energy via redox reactions induced by the lithium ion intercalation/deintercalation
Data Source
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AI summary
Disclosed is an electrode active material comprising: a core layer capable of repeating lithium intercalation/deintercalation; an amorphous carbon layer; and a crystalline carbon layer, successively, wherein the crystalline carbon layer comprises sheet-like carbon layer units and partially or totally comprises multilayer sheet-like carbon layer units. A secondary battery comprising the same electrode active material is also disclosed. The electrode active material can inhibit variations in volume of the core layer that may occur during repeated charge/discharge cycles, by virtue of the interstitial volumes formed by the multilayer sheet-like carbon layer units in the crystalline carbon layer. Therefore, the battery using the electrode active material can provide improved cycle life characteristics.