L2-ESS-LITH CRITICAL POWER ENERGY Level 2 · hardware

Lithium-Ion Battery Banks

Solid-State Lithium Battery Array (SSLBA)

The Solid-State Lithium Battery Array serves as primary electrochemical energy storage, buffering daytime power generation and sustaining base loads across the lunar night, peak transients, and reactor trips. Arranged in modular, robotically swappable banks with N+2 redundancy, the cells deliver an energy density exceeding 400 Wh/kg and a round-trip efficiency above 90 percent. Integrating this chemistry into a lunar settlement requires housing the modules within thermally managed, radiation-shielded vaults. The surrounding hard vacuum eliminates convective heat rejection, while ambient temperatures dropping to -173 °C degrade solid-state ionic conductivity unless maintained within a nominal 0 to +45 °C operating range. Shielding further protects the solid electrolytes against radiation displacement damage.

Primary electrochemical energy storage using solid-state lithium-ion battery modules arranged in redundant banks exceeding 400 Wh/kg energy density

Purpose

Provide the primary high-energy-density electrical storage for the Ark, absorbing surplus generation during lunar day and delivering stored energy during lunar night, peak demand transients, and reactor trip events

Context

L2-ESS-LITH is the workhorse storage technology within L1-ESS. Solid-state chemistry is selected for its high energy density (>400 Wh/kg target), inherent safety (no liquid electrolyte flammability), tolerance to vacuum, and long cycle life. Battery banks are housed in thermally regulated, radiation-shielded vaults with modular hot-swappable packs for robotic replacement over the 100-year mission. Multiple independent banks provide N+2 redundancy at the bank level.

Principles

▸Solid-state electrolytes eliminate liquid electrolyte leakage and dendrite growth risks
▸Modular battery pack architecture enables individual module replacement without system shutdown
▸Cell balancing across series strings is essential to prevent capacity loss and thermal runaway
▸Depth-of-discharge limitation extends cycle life exponentially (e.g., 80% DOD vs. 100%)
▸Calendar aging is a significant degradation mechanism over 100-year timescales, independent of cycling

Typical implementations

▸QuantumScape, Solid Power, Samsung SDI solid-state cell programs targeting >400 Wh/kg
▸NASA JSC battery development for lunar surface power systems
▸ISS lithium-ion battery orbital replacement units (ORUs) as modular swap precedent
▸Automotive 800V battery architectures adapted for DC bus integration
▸Spacecraft battery heritage: Li-ion cells with >60,000 LEO cycles demonstrated

Lunar considerations

▸Vacuum environment eliminates fire risk but requires sealed thermal management (no convection)
▸Solid-state electrolyte avoids liquid freezing at -173C but ionic conductivity drops at low temperatures
▸Radiation-induced displacement damage in solid electrolytes is less studied; shielding is prudent
▸1/6g has minimal impact on solid-state cells (no sloshing, settling issues)
▸Modular vault design allows regolith overburden for radiation and micrometeorite shielding
▸Robotic hot-swap of battery modules requires standardized mechanical and electrical interfaces

Specifications

Functional

primary function	Store and deliver electrical energy via solid-state lithium-ion electrochemistry
inputs	DC charging power from L1-PDM bus, Charge control commands from L2-ESS-MGMT, Thermal conditioning from L1-TCS (heating/cooling loops)
outputs	DC electrical power to L1-PDM bus on demand, Cell-level telemetry (voltage, current, temperature, impedance) to L2-ESS-MGMT, Waste heat to L1-TCS during charge/discharge cycles
energy density wh kg	>400
total capacity kwh	300+ (across all banks)
max discharge rate c	1C continuous, 2C peak (30 min)
max charge rate c	0.5C nominal, 1C fast charge
round trip efficiency percent	>90
cycle life at 80 dod	>10,000 cycles
operating temperature c	0 to +45
calendar life years	20-25 per module generation (replaced robotically)
redundancy	N+2 at bank level (minimum 4 independent banks)

Physical

materials	Solid-state ceramic or polymer electrolyte (e.g., Li6PS5Cl, LLZO, PEO-based), Lithium metal or silicon-composite anode, NMC or LFP cathode active material, Aluminum and copper current collectors, Titanium or composite module enclosures, Thermal interface materials (graphite sheets, phase-change pads)
temperature range c	0 to +45 (internally regulated within vault)
radiation	Shielded to <0.01 Sv/year within vault (regolith + structural shielding)
dust	Sealed vault; no direct regolith exposure
vacuum	Vault may be pressurized with inert gas (Ar/N2) or maintained in vacuum with sealed modules

Operational

power consumption w	50
thermal range c	0, 45
lifetime years	100
mtbf hours	200000

Interfaces

Provides

→Power Distribution & Managementpowercritical
DC power discharge from battery banks, up to 10 kWe continuous per bank
→Battery/Storage Management Systemdatacritical
Cell-level voltage, current, temperature, impedance, and fault status telemetry
→Active Thermal Control Systemthermalessential
Waste heat generated during charge/discharge requiring active removal

Requires

←Power Distribution & Managementpowercritical
Regulated DC bus power for battery charging at controlled rates
←Battery/Storage Management Systemdatacritical
Charge/discharge commands, rate limits, cell balancing directives, and mode selection
←Active Thermal Control Systemthermalcritical
Active heating during lunar night (maintain >0C) and cooling during high-rate charge/discharge
←Primary Structuremechanicalcritical
Battery vault structure, module rack mounting, and regolith shielding enclosure
←Robotic Operationsoperationalessential
Robotic module extraction, insertion, and connector mating for hot-swap replacement