Core-Shell Anode Material with PTC Shell for Lithium Batteries
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Solution Overview
Problem
Current anode active materials for lithium secondary batteries fail to balance excellent electrical characteristics with sufficient safety, leading to a need for an improved material that maintains performance while enhancing thermal safety and conductivity.
Innovation Solution
A core-shell type anode active material is developed, featuring a carbonaceous material core coated with a shell containing a Positive Temperature Coefficient (PTC) medium, such as barium titanate, and optionally including spinel-type lithium titanium oxide, to enhance conductivity and thermal safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If natural graphite is used as anode active material, then low cost and excellent initial discharge capacity are achieved, but charge/discharge efficiency and capacity rapidly reduce when cycles are repeated
Solution Approach 1:
The invention uses a composite structure consisting of natural graphite particles coated with a carbon-containing resin layer. This composite material combines the high capacity of natural graphite with the stability and conductivity of the resin coating, preventing the rapid degradation that occurs with pure natural graphite while maintaining low cost.
2Reliability
If non-graphitizable carbon is used to improve safety and capacity, then excellent safety and large capacity are achieved, but particle size becomes small with micropores leading to lower density and poor commercialization
Solution Approach 1:
The invention creates a composite where non-graphitizable carbon provides the safety and capacity benefits, while the carbon-containing resin coating fills the micropores and increases the overall particle density. This allows achieving excellent safety and large capacity without sacrificing commercial viability through improved density.
3Reliability
If lithium titanium oxide is used to improve safety and durability, then stable structure and excellent charge/discharge cycles are achieved, but battery characteristics reduce due to low average voltage
Solution Approach 1:
The invention forms a composite structure where lithium titanium oxide provides the stable spinel structure, excellent durability, and safety, while the carbon-containing resin coating improves electrical conductivity and maintains higher average voltage. This composite approach allows utilizing lithium titanium oxide's reliability benefits without suffering from its low voltage drawback.
4Volume of stationary object
If mesophase-based graphite is used to improve fill density and energy density, then high fill density and improved molding are achieved, but reversible capacity becomes low
Solution Approach 1:
The invention creates a composite where mesophase-based graphite provides the spherical shape, high fill density, and good molding characteristics, while the carbon-containing resin coating contributes to improved reversible capacity. This allows achieving high energy density per volume without sacrificing reversible capacity.
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 core-shell structure improves electrical characteristics, thermal safety, and high output density, effectively addressing the limitations of existing materials by providing both high performance and safety in lithium secondary batteries.
Implementation Method 1
a shell formed outside the carbonaceous material core, the shell comprising a PTC medium
Implementation Method 2
The core-shell type anode active material for lithium secondary batteries comprises the PTC medium in the shell, and thus has the improved conductivity
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3(a)~3(b)
AI summary
Provided are a core-shell type anode active material for lithium secondary batteries including a carbonaceous material core; and a shell formed outside the carbonaceous material core, the shell including a PTC (Positive Temperature Coefficient) medium. The core-shell type anode active material for lithium secondary batteries has the shell including the PTC medium, and thus has the improved conductivity and high output density, exhibiting excellent electrical characteristics. And, a lithium secondary battery manufactured using the anode active material has excellent safety, in particular safety against overcharge and external short circuit.